Go into the bathroom of your workplace,masturbate til your about to come, walk up to her friend and bust a nut right in her eye, then be all: "HOW'S THAT FOR GETTING IT UP, BITCH."
Post results.
Alcohol does that to you man. Just get her in the bed while you're sober and drill her brains out.
Personally I would just go for it again, then ram her until she can't walk straight for a week.
The best excuses are...
1. She was to ugly and couldn't get you erected.
2. I was to freakin drunk to even know I was about to get laid.
Simple right?