I met a girl through friends, whose personality is refreshingly attractive, so I naturally tried making her attracted back. The girl I'm talking about is around 200lbs. Based on looks alone, my usual target would be rated at a 7.
Something inside didn't allow me to think of her as only a friend.

We met on 2 occasions.
The first time clubbing with friends.
The second time,hanging at the mall.. and ended in her bedroom where we invited friends over for a party.
Once they left. I performed a massage, removing clothing down to her under garments, then left to take a piss.

When I got back, what I was about to do "hit me," and suddenly I was repulsed, as I had never imagined I'd be doing a 200lb woman, let alone not a 7.5, and out of desperation I started fishing for excuses as to why I "could not go on."

I know to be honest, and upfront, but I know that to tell her I stopped because she's such a large woman would attack her image insecurities (unless she secretly doesn't have any).

I feel it was right of me to follow my attraction, but is there a certain place before being in bed with her that would be beneficial to end it at? If so, where, and how might you do it?

Also, I'm still in a clusterf*ck. What might be some steps to improve my current situation.