Do you live with her? If so, she'll probably find out that your tits are growing and hormone pills are at the place anyway. Just don't say it directly to her face and don't start hysterics like a little girl it's never gonna work. You need to gradually expand the overton window by introducing such topics into your daily communication and watching her reaction. If she's completely against all of this, you'll have to move out and live on your own. If not, continue expanding the overton window until she has to accept it.
If you do everything right, you won't destroy your relationship with your mom in any scenario.