Caleb wees more after the first feed in the morning that he does all night. I sleep him with both boosters and he is never wringing wet even if he sleeps 12 hours. I change him and use the same combination of two boosters and he is soaking at his next change. He usually gets quite grizzly if he's really wet though it is better for him if I use a fleece liner.
If you're getting up to her for a feed than you can change her then to see how her wetting pattern is.
I've never been able to have a disposable on any of my boys for as long as 4 hours without them getting a rash so I don't know any different IRT frequency of changes.
My daughter is the same. She is a Super Soaker after her first and sometimes second feeds of the day, so I find myself boosting at those times atm. The only time I boost at night is if we have given her a formula feed in the afternoon, as she tends to drink practically the entire 240ml.
We also use the small snap insert, but won't use the long one until we are no longer using the 'small' setting for the nappy.