Yes, some girls wax their stomachs. Whether or not to remove belly hair is a matter of personal preference, and waxing is one of the methods used for belly hair removal.
There's no medical reason to remove stomach hair; it's purely cosmetic. If a girl chooses to remove it, waxing is one viable option. As stated in the provided reference, "There's no medical reason to remove the hair from your stomach — it's purely a personal preference. There are several ways to remove belly hair, including: waxing." (07-Jul-2020)