Pitbulls are high energy athletes especially when they are young. So if your pit is only getting those two 45 minute walks with intermittent play then your just not expending close to all her energy. I found the trick to using up all that energy is getting my girl to sprint. Indoors or outdoors. I start it by getting her to bow and asking her “wut you doing!”. Thats when she knows its on. It really involves very little from me I just catch her and shake her up a little bit, roll around with her then turn her loose and pretend im going to go after her and “catch” her again. It makes me laugh to see her run off in circles or sprint around the couch, man she is fast. This high speed romp may not seem to wear her out but 30-45 minutes of it a day is enough to have a quiet gal come bedtime. I ussually don’t feed her any “meals” after 4 in the afternoon as well, other than special treats. The dinner your feeding her could be giving her extra fuel and providing all that energy you have to work off.
Sounds like you have an awesome dog though, hope this helps.