I’ll suggest that she look in the boys’ department at Walmart, good idea. DId you say the age of your girls? Hers are 6 and 8.
I have been doing this since my youngest were 6 and out of their oshgosh bibs. I had a full collection from 18 mo to 6 yo. About 25 or 30 of them that I collected from Sally’s and goodwill and friends. Both summer and winter versions. Modest, cute and combined with red sneakers and a blouse or t shirt, and hair ribbons they could play all day or shop at the food store with mom and look nice.
After 6 they went to the boys department of Walmart, the only place where one can purchase inexpensive clothing without writing or pictures on them. Plain t shirts and boy pants for the boys, and nice pants for the girls. The boy shorts do not work on the girls. I found that skorts and skirts with shorts under them worked better than the shorts available for girls. lBoys department works until the young girl grows out of them, and that would depend on development.
Remeber to tell her to buy some belts to hold up the boys pants. Buy boy belts the girl belts are for decoration.