Ok, I work in the medical field so I've heard many of your concerns before. Here's the deal, the new patch (Ortho Evra ) is over 99% effective. *As long as she uses it correctly.*
http://www.orthoevra.com/index.html
And how old is your gf? Alot of times, especially in younger girls, their menstration cycle can be off. Sometimes by a lot. And like analog said, if she took the pill and then missed her period, it's likely that the overdose of hormones is what's knocking her out of whack.
The morning after test -or your "plan B"- should really only be taking after getting a serum pregnancy test to determine whether or not she is pregnant. Otherwise it's just alot of miserableness for her that's not really necessary. A serum test can detect the hormones in a pregnant female MUCH sooner than a over the counter test. The "morning after" does not necessarialy refer to IMMEDIATELY after.
Also, the pills she took do not kill the sperm. It's too late for that. It actually causes her to have a miscarrige; which would also explain the cramping pain that she's having. It's her body trying to expell the now dead tissue (if she was pregnant). More than likely, it's just her body accomidating to the influx of hormones.
My next thing is: If you're still worried about what your mommie thinks, why the fuck are you having unprotected sex?????
Just because you're horny does not excuse you from thinking!!!
I'm sorry. I'm all for you having sex, that's cool, but be responsible next time.