If she is scamming you (and I don't necessarily believe she is, though I wouldn't rule it out), it may not even be her writing to you on WhatsApp at all hours of the night. A lot of these scams involve multiple people for more manpower. They use a girl to lure the guy in and start the relationship, and then there are more people to help her continue the scam.
I really have no idea if she really is a scammer. She might be, or she might really be a person with major issues. But if the latter is true, she is, at the very least, being deceptive and manipulative.
And yeah, you could try asking her to take pictures of the medical bills and receipts. You may be able to tell from her reaction if she's making it all up.
Just out of curiosity (and don't feel obliged to answer this if you don't feel comfortable), did you meet her on some sort of hook-up app? You mentioned it was an app for meeting people, but I wasn't sure if that meant it was an app for hook-ups or not. If it was, then it seems more likely she is scamming you.
I think you should be prepared for the possibility that she is scamming you. Even if she isn't, it's really not healthy for you to be so invested in someone who is a) thousands of miles away and b) suicidal and openly showing that she doesn't care about her own health.
If I were you, I'd ask for pics of the medical bills before making any plans for a trip. Sorry if all this sounds harsh, but there really are a lot of red flags in her story, and you've already demonstrated that you are exceptionally kind (and as such, easy bait for scammers).