Young guppy pregnancy... how far along?

Hi! So I got a guppy from a pet store almost 3 weeks ago. I’m pretty positive she was pregnant when we got her because her gravid spot was black, and since then she has gotten wider. She’s also showing symptoms such as hiding near the heater, eating more, etc. Now it’s coming up on her 3rd week and she just doesn’t seem as big as the pictures I keep seeing online. Is it possible she won’t get so big because of her age? She’s very small in length so I’m guessing she’s young, she’s probably about an inch. I know she’s pregnant, I am just confused as to why she’s not getting as big as I see in the pictures. Is it her size or is she just not as far along as I thought?

This is what she looked like a few days after bringing her home. As you can see the gravid spot was dark and she was still showing signs of pregnancy as previously mentioned, but just not as round. This was 2 and a half weeks ago