Lets give it a try

Originally Tom had decided that he was not going to entertain Sarah's suggestion about trying to change Matilda. It was just didn't seem workable. Wishes effected her not other people. Having seen Matilda dressed in that slutty outfit he was going to reconsider it. Her tits had almost been visible through that top and those shorts made that tiny arse look amazing. How could that little vixen be the same almost boy like girl he had had dinner with? He knew arousal was a danger to him. It always sapped away his better judgement.

He grabbed the coin and went into the spare room. Normally he would masturbate but this needed thinking about. Thinking wasn't that easy because the ladies were at it again and this time he could hear Matilda moaning and he kept thinking of her pert little tits and tiny bum. He had to be lying down though. If this worked it was going to be a big wish and he knew what impact that would have on him so he wanted to be in bed. On the plus side, he reasoned, it would also allow him to sleep through all their love making and his poor balls could recover.

He couldn't make cosmetics for Matilda. The cosmetics were nothing more than bargain body lotion, petroleum jelly and tic tacs. The power of the change didn't come from the cosmetics they came from Sarah. Then it struck him. She was already controlling her own changes without knowing it so he just needed to expand that power to effect others.

This was where he had to think. He didn't want to just ell her she had super powers as that might make reality change in a weird way or lead to strange behaviour. The cosmetics were a limiting factor. Once they ran out it was a challenge to get more and wasn't guaranteed so had to be used with at least a modest amount of caution.

It was so simple if a little hard to believe but he hoped his previous wishes about Sarah's gullibility on this subject and her ability to convince others would suffice to stop awkward questions. The existing cosmetics could work on anyone as long as Sarah applied it and the changes happened based on her vision of them. He would have to concoct a bull shit sci-fi excuse as to why it worked that way. Probably something to do with nano bots.

He settled into bed, gripped the coin feeling the tingle that meant it was active and made the wish. Darkness swept over him and he didn't wake until morning.