If you were about to have sex with a girl (her first time) and she freaked out, what would you do?

Yeah seriously at any point if she says stop you better stop. No just because you respect her wishes as you should but you could be accused of rape.

I'd probably laugh my head off! Hahahaha. I would be patient with her but only to an extent. If it never leads to any sex at all, I would break it off after say, oh, two months or so. The good news is that at my age, no virgins will be found so I won't have to worry. But if this were to happen back in my youth, I probably would have laughed hard and long on it. Thankfully, I am more even tempered and level headed in addition to being sober so I would calmly walk away.

Then I'd be slightly upset (^_^)

Morally and legally, no means no whenever she decides to say it and you should follow her wishes.

I can also understand that you would be angry if that happened but you need to manage that emotion. Hopefully you just walked away from the situation.

I guess you're left with a choice now; either carry on with the relationship or move on. I think you will appear pretty shallow if you walk away because she said no but that is your right in this too.

It is easy for you but to a girl/woman it's harder, Do you mean virgin? If so.
It's going to be her first it will hurt and you need to think about this, to her it might be a big deal you're her first! For men it's like sticking you're dick in apple pie. See the difference lol
Talk to her tell her she doesn't have to do this until she feels ready!