my holland, Gazzles, was definitely bigger than that by 3+ months (I found she did the fastest growing between 8-12 weeks)... but then, she's turned out to be a bit on the larger side as hollands go (over 4 lbs as an adult).
the important thing is whether she feels appropriately filled-out for her frame, since if she's got a smaller frame, it's totally normal for her to weigh less. if she doesn't feel too skinny, her appetite is good, she's being fed a decent amount of pellets for her size and age and she's got unlimited access to hay, then there's nothing wrong with her and absolutely no reason for concern. as oakridgerabbits said, she's probably going to be on the low end of the "normal" range for hollands as an adult.