Dating her best friend
Their relationship is between them; it's not your cautionary tale or your soap opera. It's easier, of course, to have hard-line rules — "exes are never OK" versus "exes are totally fine" — but that's not the world we live in.If they choose to share details with you, that's fine — you don't need to stick your fingers in your ears, unless an overt comparison is being made (see No. Your relationship and theirs are separate things, and you don't need to know anything they don't care to tell you. If someone seriously mistreated your friend (we're talking emotional or physical abuse, infidelity, lying, stealing, etc.), don't date him, no matter how awesome his butt looks in jeans.Queer communities are often small and insular, and once you've found one, you tend to hold on to it for dear life.It's difficult to meet people you're romantically interested in beyond an already-defined circle, and outside of your city's queer scene, most people you run into are likely to be straight.
The reverse is also true; no matter how much you love discussing your dude with your besties, his ex can probably live without hearing the details of his current sex life. It's OK to come to your partner for advice if you're arguing with your friend, or vice versa, but absolutely resist the urge to belittle or insult one of them to the other.
We know our backstories will be tangled and intertwined.
I can count the degrees of hookup separation between my closest friends and myself, and usually come up with no more than two or three.
If you need to vent about one of them, find a neutral party. But don't assume she doesn't want an invite if you haven't asked!
In general, allow your friend and your sweetheart to decide how much contact they want with each other, and don't push them to associate if they're not into it.