I'm going to fall asleep in my girlfriends lecture
Why would you fall asleep during her lecture?
She is boring and doesn't know how to teach.
I know that some subjects can be boring, but falling asleep while your gf is giving a lecture is inconsiderate. Do what you have to do to stay awake and show respect to her.
It's not that big of a deal...
I just think if you fall asleep while she is teaching then she'll be really offended.