I met girl through a friend but the two have fallen out, I still want to see both

I'm good friends with a lesbian girl who I met in a club, I was dancing with her thinking she was into me until she dropped the gay bomb on me but I still gave her my number as I thought we could still be friends.

We hanged out quite a lot just doing normal stuff, its like hanging out with a guy inside a hot girls body but somehow out friendship works anyway

So she asks me to a house party she was having, I turned up but I didn't know anyone. I got talking to one of her friends that I ended up sleeping with, we started seeing each other and is starting to go into beyond friends stage.

I found out that my friend and this other girl have fell out (I don't know why) but I really like the girl but would never of met her if I didn't met my friend and feel like going behind her back as I haven't told her yet but the girl has done nothing wrong me and still wants to see me.

What do suggest I should do? so I don't fall out with both.