I would guess (just from thinking about the adult size) that probably around 5 or 6 pounds is pretty usual for a 7 month old female, but I am no Mau expert. I would say ask the breeder(s) of the kitten, and of the dam and sire about what is typical of the breed and of that line. Not that that will tell you exactly, since they can still come in a range of size. I wouldn't worry about it if she is eating well and in good body condition, not too thin or too fat. ( that is something the vet can tell you if you are not sure how to assess it, and there are body condition charts online. http://www.pet-health-care-gazette.com/2010/05/16/cat-body-condition-score-chart/ ) Cats can go through different phases of growth on their way to growing up. If she seems small now, she might still put on a growth spurt in a month or two.
She is still growing at 7 months and should be let eat as much as she wants. If you feed a good-quality diet with very little carbohydrates she shouldn't get fat.