That is so ODD! It’s usually the teenager pushing for less modest clothes because they’re trendy, and the mother, seeing the sexual provocation, trying to hold her back! Just goes to show that generalizations don’t always hold true for everyone.
From the point of view of me as a young woman: I developed (breasts and first period)
really early, and I started a terribly bad habit of reading romance novels at a very young age, some of which were rather more explicit than a 10-year-old should really be reading. For either or both of those reasons, I felt very self-conscious walking around in public, feeling like men were looking at me in a sexually appraising way – perception or reality, who knows – and the LAST thing I would have wanted was to dress provocatively and actually INVITE men to look at me in a sexual way.
From the point of view of me as a mother: Now I am 37 and the mother of three girls (and two boys), the oldest of whom is 11 years old. Thankfully, she is developing far later than I did and is showing no interest whatsoever in romance novels (whew) so I think she is enjoying a longer, far more innocent childhood than I experienced.
As a grown woman, wife, mother, and a chastity speaker who has watched videos and read many books and articles on the subject, let me tell you, whether it’s fair or not, modest dress is a very important part of how men will look at you and treat you. We have to face it, men are just psychologically hard-wired differently than we women are. They are FAR more visually stimulated than women are. What is a “cute outfit” for us may be very provocative for them. So out of concern for the spiritual welfare of our brothers in Christ, and for our own safety and emotional well-being, we could put a little effort and thought into how our dress affects the men we encounter day to day, whether friends or strangers. Think of it this way, some young girl may be dressing in a trendy / provocative way hoping some guy at school will find her attractive, but the 30-, 40-, 50-, 60-, and 70-year-old (!) guy walking by on the street gets to see the same outfit and think “interesting” thoughts about her, too. Creeps you out, huh? Well, it should.
I recommend Wendy Shalit’s book A Return to Modesty
amazon.com/RETURN-MODESTY-Discovering-Lost-Virtue/dp/0684863170
Colleen Hammond’s book Dressing with Dignity
amazon.com/Dressing-Dignity-Colleen-Hammond/dp/0895558009
and from a guy’s point of view, Jason Evert’s book If You Really Loved Me
amazon.com/You-Really-Loved-Questions-Relationships/dp/1569553696
for some ideas on where to draw the line in dressing modestly, but more importantly, WHY to dress modestly. Showing skin is not the way to demonstrate “grown up”-ness; self-respect, self-control, and consideration of others is the way to demonstrate maturity. Your lack of comfort wearing certain outfits (halter tops, tank tops, bikinis) is all you need to say NO to them. But don’t worry, this won’t always be a source of conflict between you and your mother. Soon you’ll be out of the house, employed, self-supporting, and buying all your own clothes!

Seriously, though, best wishes as you and your mom iron out this issue between you.
Christine