You really should have been reading more in the thread, including the recent posts in the thread on this page. Relevant points that may relate to what you say could be missed otherwise. If my points were considered, it might be seen it is not good to make a demand for what would likely contribute to cancer. And it is all for cultural values that shift. It is all over nipples being noticed, but why, except for values in our culture that shift? In the Bible times, and in the centuries previous to the twentieth century, bras were not even around to use.
I had said these points with information that can be checked out. If the mother flirts with the daughter's boyfriend, or if he shows real interest in the mother, those are other issues and those should be dealt with, probably either with keeping the boyfriend away from the mother and going somewhere else, or with dropping the boyfriend if he is part of the problem. But expecting the mother to change with what can contribute more to cancer is not right, and her not having them should not be thought to be the problem. Bras are not benefiting health, and it is not good for them being worn more.
www.BraFree.org
Some sites dismiss this saying their study shows no link, but there is vested interested that protects current marketing. The original study was conclusive enough to show such link, and with bras not being used pectoral muscles that become weak are strengthened enough instead, and rather than sagging that will occur as believed, that is avoided with such strengthening. In the end, it is only cultural values that are an argument for women needing to use bras, and this sexist separate requirement is not better for them.
It is not for us to say what should be demanded for how another's parent should dress, that is inappropriate, and wearing what likely contributes to getting cancer should not be valued at all. We can get over seeing how the form of women's breasts appear, as it happens in other cultures. If the daughter has a problem with her boyfriend there, there are other places they can go, if she really should stay with him.