I seriously doubt an XT4.5 would notice the weight of a Telrad (or heavier optical finder). The CorrecTension springs are quite firm and keep the scope wherever it's pointed. I would strongly recommend the Telrad for you and your daughter. The many printed and online resources that furnish Telrad circles REALLY help beginners find their targets. The XT4.5 is a great starter scope that I've recommended to several families with young astro beginners.
As a side note, a Telrad is extremely easy to move from scope to scope with the purchase of additional bases. Telrads are #1 in the world for a reason.
I had one for a while and one of the first things I did was to release some of the spring tension by using key ring extensions. I think there is some good latitude with the tension.
They are relatively light. While I never weighed mine I have no reason to doubt the Orion listed 17.6 lb weight. It was so easy for me (as an adult) to snatch this up with one hand and pop out the door to view. The handle was also in a decent location...not real awkward and fairly well balanced.
My only complaint about the finder was the same as the focuser. Not a great height for an adult! Nevertheless I enjoyed using it with either a low stepstool or a stadium seat pad - whichever was most convenient to grab at the moment. The optics were really pretty good and it was a breeze to collimate because you could look through the eyepiece at the same time you were making adjustments. I took mine to several public events and kids gravitated to it. It was a Goldilocks just right. Our club now keeps one at our observatory site.
One minor issue is that it has a slight tendency to want to tip when altitude is changed in a ham fisted manner. This is because of the low weight of the base ( not a bad thing if you want portable) and the position of the altitude bearings. Mine never toppled because it was easy to sense when it felt it might want to try that and it was instinctive to back off the pressure. Using a moderate touch always worked fine.