There is a certain kind of bra that adheres to the skin using a sticky substance. There is no strap on the back, the sides of the bra end underneath you're armpits, which is where the sticky stuff is that keeps it on.
Some girls do wear a bra with a dress it all depends on what kind of dress it is. like if it is a strap less dress then don't but if there are some straps then usually you do.
The best bra for a halter or strapless dress would be a convertible bra or a strapless bra. Try the Vanity Fair convertible bra which allows you to choose how you want to wear your straps!
first of all how is she if she is a girl she should be wearing underwear,Bra,shirt,and pants/skirt or a dress!
you should wear an under shirt if you can see your bra.
When you wear dresses like tank top or strapless dress then there is need to wear transparent bra straps.
I sometimes do, but some of my sun dresses have built in pads.
You can wear training bras
A bra is for support and a slip is to make sure a dress is not see through. If the girl already wears a bra, and she needs a slip, she can easily wear them both. Depending on how much support and the dress she needs, she could choose to wear only one or the other.
a strapless bra
Yes, it is weird and it would look tacky to do so. Go to a department store and buy a bra to wear with a strapless dress. Look in any fashion magazine and you will see that it just isn't done to have a bra with straps showing in strapless dress.
Your underwear & maybe a bra (depending on how the dress is built). For example, some dresses have a bra or push-up bra built inside; others are very strappy or have none at all, so not wearing a bra or wearing a strapless one would look better.
It's not because it feels good. It's because no one wants their bra to be visible under the dress (which it would be if the dress was low-cut like you mentioned.)