I'm sure this was an awkward situation for you and your mother ... I'm not sure why it needs to be talked about though. You don't need to tell your mother that you masturbate, and you certainly don't need her permission.
It is normal for girls to masturbate. It's also normal for girls not to masturbate. It depends on the individual (and this goes for guys, too).
Putting your finger into your anus isn't going to be harmful to your body as long as you're not hurting yourself (and if you are, you'll feel pain and should stop).
I'll move this to Sex Basics, b/c i think it fits better over there.
There isn't anything socially unacceptable about a female pleasuring herself. If there is, this world is more screwed up than I thought.
Keep in mind though, that your mother probably masturbated too, or do something of the sort, when she was your age and younger. She may have just been a little shocked, but I don't think it was a bad shock.
Chances are, your mom will never bring it up. Although I'm a guy (which, might I add, makes no difference to the level social acceptance or anything), my mom's walked in once or twice whilst i've been masturbating, and has never mentioned anything afterwards. Its easier that way.
I wouldn't dwell on it too much, Nicky.
It may seem like a big deal, but its really not at all. Just one of those things.
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