My mom is having surgery tomorrow for a fractured hip. How long is this surgery?

Every person is different and there are many variables once they open her up. You should try to talk with the surgeon or other doctor who can fill you in on her particular case. I can see you are worried - with good reason - because her age puts her at risk. But if the surgery is necessary, there is little we can do. My thoughts are with you.
Carol

All surgery's are different, and my relative's surgeon also did a partial hip replacement at the same time (he was head of the ortho department in the teaching hospital she was sent to, and he says there is a better outcome with elderly patients, if they receive a partial hip replacement at the same time) as inserting a plate to fix the fracture, but it took about 1 1/2 hours. But ask. They always tell you how long a surgery will take, and they are usually generous in their time frame.

I've come to the conclusion that if the person likes to walk before the hip break, then they'll be more motivated to walk during recovery. At least that was true for my mother-in-law. And getting up and walking when they get to rehab is absolutely essential for them to get the heck out of there and move on.