We've been friends for nearly 8 years now, and we had a physical-type relationship at one point. We've since become "just friends" but she's made it pretty abundantly clear that she'd like to be more, and has started also to be more physical with me- sitting closer, flirting and holding me longer than usual. I'm having a hard time saying no, I think partially because of our history. I have a hard time telling what my feelings are for her. I didn't think of us as anything other than friends until this point.
At the same time I don't want to shatter her marriage or our friendship. She's married to a great guy who really genuinely loves her and her kid. It's also stressful on our friendship- I'm always questioning every little thing now, and I feel like I'm either walking on glass or contribiting to an affair. I know I should back away, but it seems like every time I do, she has another severe depressive episode. On top of that, she's my best friend- and I don't really want to end the friendship all together.
What behaviors are appropriate? What behaviors should I absolutely stop? Do I just back away all together? I don't want to be "the other woman" here. I just want to be a helpful and supportive friend. How do I back away without withdrawing completely?