I'm surprised Touma isn't holding on to her with his right hand. If she got offended and tried to shock him in this state, she could. If Touma was holding onto her left wrist with his right hand, she wouldn't be able to shock him.
Of course, neither of those scenarios would be able to protect him very much from a kick to the crotch by an enraged Mikoto if she's insulted by his offer.