I'm not sure how long it should take, but I don't think I would feed her the same ammount you feed Max. I would feed her what it suggests for a 65 pound dog (since that is what the vet figures her ideal weight is). Then she won't gain it too quickly and you won't have any problems cutting back when she reaches the weight you want her to be.

Maybe you could weigh her every couple weeks so you can keep an eye on the weight gain? Then adjust the food accordingly.