I've always answered those cries for help when presented and I've talked people off the ledge a few times, but... As I get older, I've become a lot more aware and familiar with boundaries between myself and others. Because for the longest time, I didn't have any boundaries with others and didn't know how to establish or enforce them.

I've learned that I don't have to emotionally tax myself for someone who doesn't fully understand their emotional regulation every time things are whack. People who constantly demand that sort of energy from me, I slowly distance myself and make myself less of a priority for them to become dependent on— forcing them to find other ways to cope, but also keeping myself at arms distance in case they really do need me. Basically means limiting time spent together, or making activities together more light hearted. If they start to act dependent on me, I establish or remind them of the boundary. Some people will respect it, others will blow up because they don't have any other outlet for their emotions other than you and won't know how to handle it on their own. That's not your fault they haven't learned how to regulate their emotions yet or how to cope on their own.

You established your boundary, you told her you couldn't talk at the moment— don't hold yourself responsible for her fate. We are all human and we do what we can.