OK here we go :
1. Take her out at night before crating her. Give her 10-15 minutes until she pees encouraging her all the time with words like "go" or "pee". When she is done parise, praise, praise and treat. No water before she goes to the crate.
If she doesn't pee, take her back in to her crate.
2. She goes out very first thing in the morning even before you have your coffee. Same routine encourage, praise and treat.
3. She should go out after each nap and each play session.
Most important thing is consistency and routine. With my puppy, he is now 8 months old, he sticks to a 5am -12 pm - 7pm routine. He goes out at 5am to pee. 7am to poop [ after breakfast at 5.30 ].
Generally speaking a dog will not soil where she / he sleeps. Also, a 3-months old could hold herself up to 4-5 hours but in your case don't push that long until she knows that peeing in the house is wrong.
If she is with you all the time but manages to slip away, I would put her on a leash even in the house so wherever you go she goes.
By the way :
1. what have you done so far to train her ?
2. Where does she poop ?
3. What do you do when she pees in the house ?
4. Have you ever caught her peeing ? If yes, how did you react ?