Question: Women’s stores have in them a room for changing and measuring. So if a woman takes off her clothes to measure herself [with the clothing]. does this enter into the prohibition?
Answer: No, No. First. the likes of this action that a woman enters in a place where there are men, this is not adequate. If there is a place specific for women and there is only women and there is a door specific for women in the market, no one enters it except women only, then this is not necessary. As for her taking off her clothes and measures herself, [then she does so] without stripping off her clothes.
[Taken from Sharh ibn Majah no. 267]
Faisal ibn Abdul Qaadir ibn Hassan