OK, I went shopping with my mom today, and she had me try the clothes on while she was in the dressing room. I asked her if I could have some privacy, and she said, "If you have a bra on, I'm coming in." later I asked her, if that's how she thinks, why can't I wear a Bikini? Arnt they the same?
People aren't looking at your bra in public, so she doesn't want them looking at you in a bikini in public. It makes logical sense, but in reality it is a bit strict. Moms are moms, though. Nothing much you can do about it.