You are 10 What is a period?
A period is something girls get every month, it gets rid of bad blood and eggs and tells a girl (now a women) that she is able and ready to have babies.
That depends if she is new to the whole period thing. When I was ten I got my first period in August then my second in November. But some 10 year old girls, that had their period, will get their monthly period and some will have irregular (which is normal after your first period.) So that is a 50/50 chance.