Tell her truthfully

You had a number of ways of going about this, but... No you couldn't lie to her like this. I mean you could, but that would require so much changing of EVERYTHING that you'd lose all that this relationship would mean. "...So... I kinda gained the powers to change things and... Thought this may have been... entertaining as the first change.

Claire huffed "The first thing you changed were my tits?!?" feeling outraged in her body being changed like she was a lump of meat... Then again this was kind of exciting and it wasn't like she hadn't tried flaunting her pillow tits and hips when they were younger.

"Well." You said as you noticed her spike of anger start to simmer "...I mean I was a little... curious... and it's only for this game! You should shrink back after the next round."

Claire tried staring you down a bit as she puffed up her chest which require significantly more effort to do but also was a bit more intimidating "Well alright, on one condition. I get a free change on you, and no more cheating in our games!" You nodded "Well ok then. For the next 2! Games you'll shrink to the size of my hand from the bottom of my palm to middle finger." You weren't entirely sure what Claire was up to but you nodded as you walked to the game table and lifted a leg of yours up and you stepped onto the table as your legs shrank to the size of small sticks and then the momentum carried the rest of your shrunken body as you tripped and fell arms first onto the table which looked... Big. A slice of pizza that was on the side would probably take you a month at least to consume assuming it hadn't gone moldy, and the die... It was going to be tricky rolling both. Picking yourself up you noticed Claire leaning over you her large breasts looking closer to a wall.

"Well aren't you quite the cutie like that? I think it's about time we picked our next game. How about Jenga?" Claire said smirking a little.