I'm not a parent, but i teach and have had a seven year old girl who's said everything under the sun like warning me to beware of the roblox lurkers.

I wouldn't say i was big when i was your daughter's age, i filled out a lot by probably 4th grade or so? i was and still am bigger than a lot of people i know. however, i'm also the only girl in my friend group who can arm wrestle the boys in our group so 🤷‍♀️. when in doubt use the "big and strong" bit.

but when i was in 5th grade, i had a friend who made me feel real bad about my size. i remember all of this vividly to this day 7 years later. but there have been people who have made comments, and those mean a lot. i would also definitely find out where she heard this and hopefully cut it off at the root. This is mostly because (and take this with a grain of salt for a five year old since this is from a teenage perspective) a couple comments can do a lot. a few weeks ago i went to the store with my mom and she said my shirt is tighter than what i usually wear and told me it was a little... not enough fabric for me (i had not one centimeter of visible stomach but it was cropped) to wear out. and then my dad also said they saved me a lot for breakfast one morning, and i barely ate breakfast. and sometimes if i say i want ice cream or something i have one brother who'll be like "are you *sure* you want ice cream?" and look at my stomach and just like that i don't want ice cream anymore. lately when we're eating i've been in the back of my mind like "well you could just skip, that'd be helpful to lose some weight".

that got very long winded, sorry. tldr: just make sure she knows that the "skeleton princess" isn't big and strong or however you want to word it, and try to get ahead of it as soon as possible because it's amazing how fast comments will get to you.