German Shepherd Q&A
It is hard to tell, but that seems small. I have a 4 month old female that is 70 pounds
Some lines grow more quickly than others. At her age there is no way to tell what she will mature at. Ask her breeder if she is from a quick or slow growing line.
I have a 9 month old 100 lb female. She is on the smaller side and seems to be about 20lbs or so behind on the typical growth charts for Mastiffs. She was rescused from a bad puppy mill situation when she was 11 weeks. I believe the bad start in life slowed her growth down but she is catching up rather well.