I just got a new tortoise and it is 8 months old. She seems to be sleeping a lot and I don't think its normal. How long or often should a tortoise sleep?

It depends...

you should have a heat lamp.

if so, it should be on from 12 am to around 4-5 pm. this will stimulate your tortoise and get it to bask, it is also common for them to sleep while they bask.

What species of tortoise is it?

a tortoise should sleep about 13 hours a night to poperly have a good sleep, but also they take long extended naps during the day.

What are you feeding it, and how often?

I hope this helps you...

Cheers!