Except you can.

You just shove her off, get up, and walk away.

That's the power dynamic between the sexes, you can leverage your (generally superior) upper body strength at any time (unless you've been roofied), and leave.

That's why putting your arm on a door frame to block a woman's exit can be construed as sexual harassment, they have to wait until you decide to let them leave.

Don't feel guilty for defending yourself, you have a right to bodily autonomy. Nobody is gonna protect you but you.

Also you can leave out the girl's description, it's irrelevant how fat or ugly the she might have been. You already said she wasn't your type and it just makes you come off as vain.

Your buddies were probably annoyed listening to your whiny-ass story about how you were too terrified to defend yourself because of something that will probably never happen. Sack up and squeeze out that beta-energy.