My daughter getting her period and not telling me?

My 10 year old daughter I think got her first period because ive been finding a little bit of blood on her underwear. Im going to talk to her about it. She doesnt need a bra or doesnt have any armpit hair etc. Im not sure if she got it though becuase she hasnt been angry or wants to be alone or any of the symptoms. Do u think she has it?