Have you considered the fact that you know she's a lesbian, and you two are friends - you're 'safe', she likely doesn't expect it to become a thing, because she doesn't swing that way, and she knows you. (Or thinks she does?)
I'm asexual, but I'm no virgin. (I fed myself 'you won't know until you try' until I almost bought it.) I honestly did not give the sexual portion of the relationship another thought once I was out of the bed. (Said 'relationship' did not last long. I wasn't even surprised at the time, or upset. Relieved, more like.) Your friend may have a similar 'sexual blind spot' for men: it was a thing that happened, it wasn't bad, but that may be the extent of it.
Just, look, don't buy into 'she slept with me, therefore she is bi', if anyone tries to convince you of that. Sex and sexual attraction are two separate things. If she says she's a lesbian, she's a lesbian. Inserting Tab A into Slot B doesn't prove anything. (For one, strap-ons exist.)