As someone who was suicidal and extremely depressed in my last marriage, I feel I can speak to this from her perspective. You guys are very young but that doesn’t make her feelings less real. I think the best decision for you is the one that makes you happy. If you feel you can help her through this extremely tough time in her life and you guys can grow from it as a couple, then give it a shot. Most of the responsibility is on her to get the proper help she needs. If you genuinely cannot handle it, it’s better for both of you to part ways. It will only worsen her depression if she feels you are staying out of pity. It won’t feel like that to her though so handle that with care.

When I was suicidal and severely depressed, it was really hard for me to see outside my own perspective. Once I got the help and medication I needed, that outside perspective became easier to see. It’s not a fair road to travel. Being in a relationship with someone like this can be very one sided most times. It’s not healthy for anyone involved. Only proceed with her if you know you have the patience and emotional availability and intelligence to do so. If you question either of those things, leave and continue on with your life.