Yep, I also think at 7 months you should at least having fun most of the time. I understand that once you land in a supporter’s forum, it’s because it’s not being fun. And you aren’t here to describe the nice moments. If she’s been diagnosed with BPD, it’s not a matter of couple’s therapy. It’s a matter of HER therapy. And perhaps yours too for codependency. I’d suggest you two start therapy on an individual basis and stick to it. Keep your therapy spot for yourself, not mixed up with that person.
PTSD/BPD might well blame you whether you want to spend time with them (you’re being sticky) or not (you don’t love them). I did that quite a lot myself. So, just don’t change what YOU want and find out what you want, what you like, what you don’t like, what you concede, what you’ll never accept and will make you leave at least for a few days. Boundaries don’t work if you can’t enforce them. For each crossing, there is a readjustment and frankly, for some of them being disengagement. She might (and probably will) understand that like a petty retaliation against her without seeing that if you don’t do this, stating boundaries doesn’t make any sense.
I know it doesn’t make sense neither to talk you out of this relationship. I didn’t listen to that kind of advice and I know the hope, the love, how much you want it to work against all odds. And it’s okay. It doesn’t make you a bad person. Codependency sounds super awful and it’s not a nice label. But it doesn’t mean you haven’t courage or strength.
BUT keep close to your friends. Talk about your struggles. Seek therapy for yourself, do things you enjoy. Do things that strengthen you, that don’t weaken you. Form a place where you do exist and don’t lose yourself in someone else’s struggles. Being supportive doesn’t mean to endure. And the only way you truly can help her is to be absolutely clear on what you want and how. With the acceptance towards the other person’s quirks and limitations but not in that all-forgiving, dramatic and strenuous fashion. For doing that you have to be clear with yourself too and that’s difficult.
And in any case, admit your own limitation in this. My ex did literally asked me to help him seek for therapy. The first day a crisis of magnitude happened, I said I didn’t want to see his face again before he came back with a paper stating he was on a waiting list. Which he did. But each step of the way he managed to forget his appointments, loose a document, a zillion problems before getting into it. Another time I said either you go to the ER NOW either you never see me again and I mean it. He’s got intervention with immediate follow-up which was a miracle given how that hospital was packed. The team was ready to have him as an impatient because his case looked that bad. He still managed not to get there.
I had a mandate to find it out. I read all I could about BPD and eventually landed on PTSD, CPTSD and reached… here! Which I don’t regret! Now I don’t have my ex but I have this forum! Please feel at least welcome here

Perhaps we forgot the most important!
If cost management is something she has in mind, Dialectical Behavioural Therapy books are easily available. (This one is really good for being comprehensive, progressive and not requiring you to be in a group to start it: "
The Dialectical Behavior Therapy Skills Workbook: Practical DBT Exercises for Learning Mindfulness, Interpersonal Effectiveness, Emotion Regulation & Distress Tolerance". It doesn’t replace therapy but as a start, it’s better than nothing.) They’re quite inexpensive on epub formats or even hard copy. There are also DBT groups online that generally aren’t covered by insurances but offer the advantage to be inexpensive compared to individual sessions with a therapist, but it’s heavy to implement. There is also a website called DBT tools or something alike which summarizes the DBT skills in a concise way, but it hasn’t the density of a proper workbook and isn’t very clear if you aren’t familiar with it beforehand.
There is also the YouTube channel of Dr. Fox (I’m not inventing…) who explores BPD giving tips to manage it and while I have certain reserves on certain aspects, he’s got a very encouraging, non-dismissive way to consider the problem and promote behavioural change. There also is a workbook he’s designed for sufferers and full of methods to understand oneself, manage and/or extinguish problematic behaviour. I did it for myself and I think it’s a great resource to anyone suffering from recurring problematic patterns of behaviour, BPD or not.
For supporters, there is a subreddit called BPDPartners that is very supportive to the partners trying to stick to the relationship. Another called BPDLovedOnes that is more supportive of the moment you’re wanting to depart the relationship, unfortunately it’s full of misinformation and also of raging people so it’s quite strenuous to read. On books for supporters, there is the very classic "Loving Someone With BPD". It’s very well written, it’s full of insight but at times it’s irritating because it’s so full of compassion with the sufferers that it seems to forget that yourself are quite going through a hell, even if there are moments that are validating because you can tell you aren’t the only one experiencing it.
All these are, in my sincere year of research, the best resources I think one can find regarding BPD apart from physical, committed, sustained therapy. And don’t forget that you aren’t her therapist. What I found on the web, my ex could perfectly find it by himself. But he didn’t because he still was ambivalent towards it. The fear of finding out what’s wrong with you in PTSD/BPD can really be something. I am ready to confront my old demons now but I spent years first thinking there was no problem at all, then considering that I might have a few problems, then thinking that was how it was in life in general, then facing really hard issues to understand that nope, the way I am now is impossible to sustain, … and that’s only the
beginning. Of course everyone has phases like this, but with this family of mental health issues, the reality of it you can really touch.
Sorry for the wall of text. I just hope this helps you to see things more clearly for yourself and take your best decision. For yourself and nobody else.