I was looking for bra references not expecting to draw a wire free bra, but it was one of the first options suggested, and the reviews all sounded Susan appropriate, so... Bam?
Anyway, this is the part where a bunch of women are going to potentially contact the male cartoonist to tell him what he done did wrong, but based on the information I had, it seemed a good choice for Susan.
(And though I will likely clarify this later in-comic, Susan had planned to test the effects out this way beforehand. While it's possible for someone to get carried away with a secret identity form and do something they wouldn't normally do, she decided on this in advance. Besides which, Lifeguard just makes you more comfortable with people seeing your body. It doesn't create a desire for that to happen.)