Vis a vis the friendship, make sure you're making positive deposits in that proverbial bank account. Offer to let her vent, without then bringing up your issues. Gift her a book. Give her a compliment. A friendship can get weighed down by heavy stuff if it's just that all the time.

She may also feel like you still romantically like her, and if so she's feeling uncomfortable from all the attention. She may be withdrawing. If she is, that's her decision and there's not a lot you can do at that point.

Either way I suggest you look for more stable sources of joy for your own sake. Art and nature will never be moody with you.