maybe she likes you, maybe she won't go any farther because she feels it would be like betraying her friend...
you say "several months ago" your ex left, and "several months after she left (left the state?/left the relationship?" you started talking to her friend. I'm confused just how long you've been talking to her friend and how soon after you broke up this happened...
In my experience, "comfortable" is also a weird descriptor... there have been people I've been "comfortable" with and then couldn't stand a couple months later. I'm not trying to say this is bad by any means, just throwing it out there.
My advice with any relationship is always to take it slowly and not to do anything anybody might regret--it's generally easier on all parties in the long run.
