I find it more embarrassing if you hear your mother talking to you and reply only to be met with the realisation that it was a random stranger talking to somebody else
One time, I was trying on this strapless dress for a Barmitzvah and the changing rooms were small and you had to go out in the store to show your parents the clothes. So I went in, got dressed. I come out and this super hot guy was sitting there. I was like "AHHHHH MOM!" Then my mom comes in and was like sweetie let me see if it fits so I took my hands off my shoulders and it slipped a bit and the dude saw part of my bra.
http://knowyourmeme.com/photos/742218-awkward-moment-seal
Hope it helped!