But she gave me no tools to move forward other than telling me to stop. If this negative talk is stemming from early childhood, I can't imagine it's much different than trying to kick a drug habit...I'm pretty sure there is much more to it than saying "stop doing drugs."
Out of everything you've said, I think this is the biggest issue. If she isn't giving you a process you can use in order to challenge those negative thoughts, then she might not have the tools herself that are needed to help you.
In some cases, regarding some things, it can actually be as straightforward as "stop doing that". Not easy, but straightforward. Like
@FridayJones was writing about, evaluating your speech habits and combing them for statements that you are not aware you are making. Anything from habitually using "I feel" instead of "I think", to inserting "kind of" into everything (example: "I feel like my therapist isn't helping me, and I kind of want to ask her if she could kind of be more specific about how I can do the things she's talking about." - I know you didn't say that, I'm just using it as an example).
And as
@Solara said, being disciplined about catching yourself right when you start to spiral into negatives.
But if you don't know any methods/processes for challenging those negative thoughts, then you will actually just get stuck - dealing with the core beliefs behind those thoughts, those are what stem from early childhood, and those take some working through.
She needs to give you tools.
Only thing I've experienced similar: seemingly out of the blue I developed a problem with hitting myself. When I was having intense intrusive memories, I would hit myself, very hard. I had never done that in my life and it was very, very confusing. It took me two weeks to admit it to my therapist, and even then, I did it in the last five minutes of the session. We were early in our relationship, perhaps five months in. When I finally managed to say "I'm hitting myself", his appeared to be very taken aback, his eyes grew wide, and he said (loudly), "Well, you better stop doing that!".
That was not his finest moment as a therapist.
I guess what I'm saying is, they do make mistakes. It wasn't til the next session that I could pull it together enough to tell him how unhelpful his reaction was, and he was glad I brought it up, acknowledged that he was completely caught off guard and that he was sorry for not handling it better. It then turned into a very productive session focusing back on me and getting at the underlying issues causing the hitting behavior. I also learned that the last five minutes is not the time to bring up the thing that I have been wanting to bring up since the beginning of the session. So, the whole exchange was ultimately productive.
I'd recommend (like others have) you talk with her about your experience of what happened. Honestly, if she's good, she will engage in that conversation openly, and she will follow through with giving you a process you can use to address your negative thoughts. And if she's not very good, she will defend herself and have an appearance of frustration and fluster. I would not think of this as a situation where you need it to work with this T because she's your second one and you won't ever find one - she just might not be good enough for what you need. So you go back and look some more. It's pretty normal, that.