Omigosh, Georgia Peach, that's awful!
Please don't even dignify your graceless co-worker's commentary with a response. If she has something to say to you that pertains to your work, it's perfectly fine to speak with her. Otherwise, just tune her out, because the fact of the matter is that she's being inappropriate with her comments.
If you stop responding to her, one of two things will happen: (1) her words will just keep falling on deaf ears, or (2) she'll realize that her words are meaningless to you and eventually she'll stop wasting her breath
If she really drives you to madness, a very simple, to-the-point response like "My body is nobody's business but my own" might shut her up and remind her of how unprofessional her behavior is.