What do women wear with low cut tops and spaghetti strap dresses?

I'd suggest choosing another type of cut, especially if you're not "small". Something more modest would be preferable and you'd be more at ease. I personally do not like that deep-V style; I can't wait for it to go out of style. If you're wearing spaghetti straps, maybe try a strapless bra from Victoria Secret or something. Good luck!