In my experience only the Moxie Teen shoes fit. I can't remember for sure but I think their feet are too big to get into Monster High.
Yeah, I just checked. Too big for MH. If you wanted to you could probably carve down the foot some so they would fit. I haven't tried it but I bet Ken shoes would fit. Also betting you could get flats for her from
Facets by Marcia. Give her foot a measure and see it they'll work. if they're a bit big you can always stuff them a little.