First, I'd have her examined by a vet to make sure she doesn't have a urinary infection. Frequent peeing is a symptom of a UTI.
Dogs vary in how often they need to pee and your puppy probably needs to be taken out more often. IMO, asking a 6 month old to hold it for 8 hours is not wise since it can lead to health problems.....such as urinary infections. Also, pets (especially puppies) should be allowed all the water they want to drink so don't control what she drinks in order to reduce peeing in the house.
If she is found to be healthy by the vet then start a walking routine of at least every 2 hours.......starting immediately when she wakes and also within 15-20 minutes after each meal. Be sure to always praise her every time she does her business on your walks.

Pets usually sleep most of the time when the owners are out of the house so they don't eat/drink as much and are less active than when you're home. That is probably why you've seen her hold it when you're gone for 8 hrs. Because she's so young, and has a peeing problem, I would suggest you have someone come in and take her for walks or leave her at a doggie day care on those long days.

Is this a small dog? It's possible her previous owners allowed her to pee in the house on pee pads and if that's the case you will have to either get pee pads or start house-training from square one by crate training her.

This post was edited by annz on Thu, Apr 24, 14 at 15:48

The minute you get home, take your dog out for a long walkies, empty your dog then take it out again ina couple of hours. Pick a phrase or command you want to use and use it while your dog is in the process of urinating. Like PP OUTSIDE. Do this WHILE your dog is in the act of going and soon you will be able to ask your dog if she needs to go. Good Luck