Q. Am I allowed to have my shaitel cut during the 3 weeks? I had scheduled an appointment prior to the tannis, but had to cancel at the last minute. My shaitel macher has a heter to cut as it is her parnassah. She advised that I ask a shaila.
A. Nitey Gavriel (Bein Hametzorim 21,5) permits trimming and fixing a wig even when one is wearing it, until the beginning of the nine days. (However, in his Bar Mitzva Seifer 22,21, he further permits the above for the mother of the Bar Mitzva bochur, before the week of Tisha B’av itself). Shevet Hakehosee (O.C. 150 ) seems to allow it at all times.
Horav Shlomo Miller's Shlit"a opinion is that it is permitted before the nine days begin.
Rabbi A. Bartfeld as revised by Horav Shlomo Miller Shlit"a