Spend time with her when you can, otherwise try to keep in touch via phone/email. Isolation and depression can form a vicious circle. But don't overdo it, either, you don't want to make her feel like an object of pity.
I wouldn't bring up the subject of suicide. If she brings it up, be honest how you feel about it, but keep calm. Don't panic, or get angry. There isn't an argument here that you can win.
Keeping occupied can reduce the effects of depression. To the extent her health allows it, encouraging her to keep involved in her regular activities or hobbies may be helpful.