It's really hard to deal with situations like this, where someone wants to be your friend but you aren't really interested in a relationship with them -- especially when it seems they don't so much want to be your friend as they want *you* to be *their* support system. There's nothing wrong with being more concerned about your life than hers. She's more concerned about her life, so why shouldn't you care more about your needs than hers?

I would probably try to taper off, answer her texts a little more slowly, not hang out with her so much outside of work, just to let it all die down.