If she was doing her job, you would not have to rub one off while on the couch. 
Listen to this man.
And btw, Slacker, don't feel bad about it. Don't let her make you feel like an asshole for jerking off.
If she gives you shit, well, tell her this....
My options are:
1) you fuck me, therefore I won't need to jerk.
2) I jerk off, no harm done
3) I fuck someone else
MEN HAVE NEEDS!