Hello Jenni, welcome to the forums. 
I'm afraid I don't have much to add to what has already been said, really, except rats do grow really REALLY fast when they are young, so it could just be that. They also grow at different rates, so it's not necessarily a good guide to compare her to your other rat.
Do you know how old your rats are? Were they kept in mixed sex groups at the pet store? Have you noticed her eating more than the other rat?
I would do some reading up on rat pregnancies just in case, as the gestation period is only about 21 days. Now would be a good time to search for vets in your area that treat "exotic" pets, just in case. It's always good to have a number to hand anyway, but now more than ever.
It might be wise to look around for potential homes for your new ratlets, too, because you could have a dozen babies on your hands, if she is pregnant.
Other than that, unless you want to take her to a vet to find out, there isn't too much you can do but wait, I don't think.
I'm afraid I don't have much to add to what has already been said, really, except rats do grow really REALLY fast when they are young, so it could just be that. They also grow at different rates, so it's not necessarily a good guide to compare her to your other rat.
Do you know how old your rats are? Were they kept in mixed sex groups at the pet store? Have you noticed her eating more than the other rat?
I would do some reading up on rat pregnancies just in case, as the gestation period is only about 21 days. Now would be a good time to search for vets in your area that treat "exotic" pets, just in case. It's always good to have a number to hand anyway, but now more than ever.
It might be wise to look around for potential homes for your new ratlets, too, because you could have a dozen babies on your hands, if she is pregnant.
Other than that, unless you want to take her to a vet to find out, there isn't too much you can do but wait, I don't think.
