Is my guinea pig pregnant?

[Jacquelineceee]

Okay, 3 months ago i got my first guinea pig, a female, from petco, it was still not fully grown so im guessing she was kind of young. About a month later I got another guinea pig which seemed almost nearly full grown, they told me it was female, until i noticed the second guinea pig was trying to mate with the first one! So now i checked and for sure it is a male! They have been in the cage together for about 3 weeks, and since I noticed, i started separating them. But is there still a chance she will be pregnant?? what should i do!? I need some advice because im worried and I dont want her to become in danger because of it!