savannah monitor question

Hello all, i just recently bought a savannah monitor from my local reptile show. if i were to guess she would have to be between 2 and 3 years old as of now and around 10 pounds. first and foremost im worried she is overweight and was hoping to get some others more experience feed back and some suggestions on what the best way to help her thin out would be.

Then the second thing i was curious about (well worried would be a better word) was i was watching her walk( or try to ) and i noticed 2 things. first she was dragging her belly and almost seemed to be pulling herself along more than walking. and second it seemed as if she couldnt move her left hind leg past the knee. when she would try to step she could pull her thigh forward but couldnt get the rest of the leg to follow through. im fairly positive she has feeling in that part of her leg because when you touch her toes or lower part of her leg she will move to either see what it is or try to move away.

She doesnt seem to act oddly at all. other that being extremely lazy and mostly just lying around in one spot untill you mess with her. but her eyes are fully open and clear looking, she seems to be watching everything that goes on around her and when she is out shes counstantly flicking her tongue and trying to explore

I was planning on getting her into a vet just to have a check up anyways with her being new and all but i wanted to get some other opinions on what could be causing this.

As far as tempatures go the cool side of her takn is between 77 and 82 during the day and around 70 to 75 at night, and her basking temp is between 110 and 120.

Ive posted a picture of her very temporary caging( 75 gal tank, 48"x18"x18") to hopefully give a better reference for her size. i will be building her a much larger cage either the end of this week or beginning of next. i am just a very worrisome person and wouldnt want to see anything happen to this awesome animal that could be avoided or helped out with so i appreciate any feed back i can get from all the learned keepers of the world. thanks again all!

I hope you built her a proper cage. Too many people buy them and end up keeping them in their "temporary" cage, which tend to be very inadequate.