Speaking as someone who was too afraid to ask her mom so instead tried to pluck them on her own and ended up with horrible looking eyebrows for years..... just ask!!!! Say "hey mom, can I get my eyebrows shaped?" and she'll probably be like "oh! sure honey"
It's worth it. Or if you REALLY can't ask, just go get them done. I doubt she'll be mad. And there's nothing she can do about it anyway :)
Good luck :)