She should have just showed them to go for the neck. If she could not throw you then she should not be teaching. I have seen much smaller people throw larger ones.
She must have been doing it wrong then.
If she usually only practices against light girls it wouldn't be surprising.
But really, if someone throws with perfect technique, it shouldn't matter that you're eighty pounds heavier. (Perhaps she shouldn't have tried a hip throw too, which actually requires lifting the opponent off the ground.)
Self defense classes are questionable. I've seen so many fliers for single sessions or a single week of them, when that is no where near enough for actual application.
It just boosts confidence (over confidence) and wastes time that could be used running.