How can I help my friend ?

My friend's wife was diagnosed with depression a few years ago when they were dating she has really bad panic attacks when she's around others she gets nervous. She also has major anxiety she can't be away from him she has to have him by her side a lot. We play in a band when we have to go do a show she gets nervous she doesn't want him leaving her she also has a mental breakdown. She's threatened to commit suicide I'm so worried for her she's my bestfriend too I dated her once she's a really sweet girl she's like a sister to me. How can I help her through this ? What should I do to her ?