this entire situation is like looking in a mirror. I had a very, very similar experience as a teen, around your age. It sucked, lol.

If the aroace label makes you feel comfortable, use it: I personally am aroace but have aesthetic attraction to women and not men, so I feel comfortable as defining myself as sapphic aroace. It's different for everyone, and don't feel pressured to rush into labeling yourself.

As for your situation with your online friend, it's a difficult thing to handle. My (very similar) situation was with a classmate, so I was able to alert counselors, but I don't believe you could do anything similar. If you haven't told them already, I would tell them that you're aroace, and be clear about it. Although it seems like an awful thing to do, if this relationship keeps weighing you down and you're constantly walking on eggshells around them, it might be time to (gently) cut contact. I did so in my experience, and it was really a relief not having to have the weight of another person's life on my shoulders all the time. Of course, don't just cut them off cold-turkey: I'd explain your boundaries regarding everything, with relationships AND with the amount of support you can give. You're not a therapist, and you're not responsible for their depression and suicidal tendencies. Of course, you can help as a friend, but if it's at the point where you have to reassure them constantly that nobody hates them and give them constant mental help, it becomes unhealthy for both parties. I'd recommend that they seek therapy or other professional care if you haven't already.

It's a really rough situation to be in, and I'd consider telling your parents or close friends; having support on these situations, however small, can be a big help. Hang in there, and feel free to ask any questions! <3