I found an exercise program called Old school new body. It has an extreme amount of information that is valid for all ages. You have to pay for the advice but only cost a dollar for a one week trial, after that it's like 29 or 39 bucks, But if what you seek is to understand just a little more about weight lifting for girls I'd just google it.
depends on the types of exercises your doing with them, stick to light weights around 1-5 pounds... no higher. I'm a boy and I lift 3 pounds for each arm 20-30 minutes a day. it keeps me fit and I don't get bulky :)