<human>: I've known this friend let's call her Virginia for around a year and a half now and she has a boyfriend let's call him Tom for around the same amount of time, I'll come right out and say it I really like her, like ALOT and from what I can tell she likes me back, this is where my confusion starts.

Me and Virginia flirt when we chat it's just the kind of people we are I know its probably not the right thing to do but its what we do, we hang out a lot during the week and make crude jokes in the pub with our friends, we're each nerds which is what attracted me to her in the first place (The common interests).

 I'm not sure how to put this without sounding horrible but she has depression stemming from things that have happened in her life (family troubles and some darker stuff that happened earlier) and due to this she sometimes will feel really crappy and depressive and I'm there for her as much as I can be, but I don't really know how to help her, I've asked and she says she doesn't know. (any tips here would be amazing)

Her relationship with her boyfriend Tom from what she's told me and what I can see is not exactly healthy they don't talk about their problems and as such she hasn't told him about her antidepressants or that she actually is a depressive, which leaves me to try and help when I have only some knowledge of what its like. She also caught him flirting online on an online dating sight but has not confronted him about it.

I'll freely admit we've exchanged pictures and have had lengthy conversations about what we'll do to each other when we're alone (as of now nothing has happened just the pictures) and pretty soon when her mothers away we plan to "play". I don't like aiding her with cheating but I really like her and don't think I could find such an amazing person again.

Another problem I have is not knowing when to stop when chatting e.g. when to stop flirting and stuff.

Please any advise would be amazing
Thank you

Provide a brief overview of the text.
<bot>: confused male likes his best friend who is in what I think is an unhealthy relationship, best friend is a depressive need help on how to help and just general tips on what to do