[It's hard to miss the family resemblance, but she still hasn't figured out that this is her father with a drastically different look.]

Hmm...I'd say a medium or a large. If you get the large you can get it taken in a little in parts. It depends on how close-fitting you want the clothing to be.

[Bulla's never seen a full blooded female saiyan, but she's going to guess a somewhat more fitted look, and definitely the most sturdy athletic clothing the store has to offer. She finds a pair of grey yoga pants and a pale pink t-shirt that seem workable, then moves on to gym socks and a pair of running shoes that look like they should fit, although they'll have to be tried on to know for sure.

Then it occurs to her that human undergarments might be an issue. No visible tail, though, so unless she's got it curled around her leg under the dress, at least finding underpants that won't fit weirdly won't be an issue. She grabs a three pack of white bikini style underpants, and then finally selects a plain white sports bra.]

There. Those ought to do it.

[Never let it be said that she isn't good at her hobby.]