I personally don't recommend purchasing a saddle before you know which horse it will always be on. Almost more importantly than how it fits the rider is how it fits the horse. You can badly damage a horse with an ill-fitting saddle.
You mentioned that your daughted has been riding a paint. These are stock horses, broad, western-bred horses. You will need MUCH wider than 4 inches. My narrow QH takes a 6.5" and my others take 7" or more (I have two paints and three QHs.) I would recommend nothing narrower than semi-QH bars for a western saddle.
Now, as far as the seat fitting her, you'll need to have her sit in some to find out what fits her best. Because people are shaped differently, you can't always generalize. The length of the thigh makes a difference as well as butt-size. She'll just need to find what's comfortable. A seat that doesn't fit will affect her balance and teach her improper habits, like perching or bracing against the stirrups. Ill-fitting tack can be the downfall of a great riding team.
Lastly, I just had my saddle re-fleeced for $90, but I don't know what it runs elsewhere.