Welcome to the site!
She holds onto the mice for 8-10 hours? If that's not a typo then there is something wrong. Also are you sure on the age? That is really small for a snake that old.
Is this a consistent issue, or are they isolated events?
Can you give us some info on your husbandry?
- cage type/cage size
- heat sources
- temperature measurement devices
- current temperatures/humidity
- any thermostats being used
- substrate
- etc.