Penelope figured she may as well go for it. If Roman didn't like her anymore after this, so be it. He was the one that proposed that flirty bet in the first place; she had nothing to lose from being herself.
And she was dying to know why he bothered sort of asking her out in the first place. They really hadn't interacted all that much and none of them had been all that positive other than that time at the donut shop.
If he liked her, she wanted to know why. And be sure that he actually liked her as she was rather than for something like her looks. She had turned more than one person that was only interested in her appearance off before by opening her mouth.
'Alright, Roman,' Penelope thought. 'Let's see what your intentions are.'
She couldn't enact her plan immediately because she didn't want the waiter interfering. She waited until their orders had been taken before making her first move.