What would have been so wrong if the screener had turned to the OP and offered to hand her the purse back, explaining that if s/he did it would then need to be rescreened? That would give the OP a choice: leave the purse where it is and pick it up after screening, or be handed the purse and have it rescreened with the rest of her belongings.

It seems that a slight modicum of common sense from the screener rather than an apparently "I'm gonna show her who's boss" attitude would have gone a long way here, especially since the OP's request wasn't unreasonable in the slightest.

While stuff like this isn't going to ever make front page news, it's attitudes like the one that the screener apparently displayed and little "I'm gonna show 'em who's in control" power trips that affect the way everyone else sees, interprets, and interacts with TSA.