I have to play devil's advocate here. I haven't read all the replies and it may already be here somewhere BUT:
SOME THINGS JUST AREN'T WORTH IT! The thing is, you really have NO idea what the lady is going through--has she just been let out of prison? Is she on parole for aggravated assault? Is she on drugs? Did her husband just leave her for another man? Who knows!
I mean, if she has the balls to cut in front of others, she probably has the balls to do a lot of things. Is it right? No. But please don't endanger your own life or your kids or hubby for some NUTZO in the fast food line. That psycho isn't worth it. Period. Karma really does work for those types.
If you want to be more in control of her Karma next time, jot down her license plate. Look it up at home and proceed accordingly. LOL!
p.s. As for her calling you fat--well, there are way worse things in life than being fat--just look at her actions!