How do you tell if a guppy is pregnant?

[SnifflySnail]

I’m pretty new to guppies. These photos are two weeks apart - when I brought this lady home (top) and about two days ago (bottom). I feel like her gravid spot has gotten larger/darker and her belly has gotten larger. I can tell her apart from the rest because she has a nip in her tail. Is this cutie pregnant or just fat?
Edit: her fins look clamped in this photo but they were not at the time or now - it was just the clearest photo I could get, she was not clamped in the rest.

 

[kansas]

If it's ever been in a tank with a male, it's pregnant.

 

[HupGupp]

I'd say you are right. Definitely a much fuller belly in the 2nd photo.

 

[emeraldking]

She could be pregnant but she could also be just fed. For a normal fed female looks also like this.