Usually because its the first time she will not have much maybe like 1-4 pups or more.
I have heard that chihuahuas have anywhere between 1-8 puppies. They usually have 1-4, but sometimes they have more.
You usually can't tell without a c-section or just wait until they are born but usually range from as much as 2-4.
My little chu is after getting preg on first litter how many pups and will she be ok we didnt want her to get preg she is over a year now and due in 2 weeks