Hi, sweetheart. Your mom will totally understand and when she finds out you're scared, she will be there for you. She can help you and answer any questions that you might have Just tell her outright and everything will be just fine. 8-)
Yes tell her. It will be fine :-) heck my daughters even told me. That was way more info then I ever wanted to have though. It's a normal thing you're going through. Let your mom help and answer all of your questions.
I'm also new to this, luckily I got mine at summer camp, so I only had to tell my mom afterwards. Just go and tell her. Your mom had to go through this, and her mom, and so on until the beginning of time. You have to tell her. I understand the nervousness, but if you don't tell her then, you won't be able to get pads you like, unless you buy them yourself, and your mother will be upset you never trusted her.