There are only two actresses credited in Brubaker, Jane Alexander who plays his friend and ally with the committee/governors (whatever they are) and Linda Hayes, who plays Carol who if I remember correctly is a bit of a goer. On this information I'm assuming the lady you're thinking of is Linda Hayes.Hope it's of use.(I've seen this film several times and can't remember this scene,I must be getting old.)
I've just discovered that Linda Hayes was born in 1918 so I doubt that it was her after all - sorry.It must have been an uncreited actress as I don't recall the lead actrees exposing anything never mind her nipples.