Mouth Quiet Guinae!

A week really isn't that long to have had her. As long as she shows no other symptoms, she is probably ok. Although I would probably take her on a wellness check at the vet anyway since she is a petstore pig.

Guinea pigs are prey animals by nature. It can take weeks or even months for them to be comfortable enough to be out in the open. If you know that petting them near their rump makes them uncomfortable, why do it? It won't help her feel comfortable around you.

Guinea pigs are considered an adult at 6 months old. If you bought her at a pet store, she COULD be sick. They often sell sick pigs but unless she is exhibiting signs, she is probably okay. Weigh her weekly and keep track of her weight. Guinea pigs will hide most symptoms of illness but the one they cannot hide from us is weight loss.