When my girls have floor time they can go nearly an hour with no poos at all and then all of a sudden they'll let loads out like they've been holding them in!
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it's totally fine. It's fine that she didn't pee either. I have two girls and Pippy will hold off as long as possible when she's on my lap and will try to get away when she needs to go, whereas Daisy will just wiggle her bum - but usually too late for me to do anything and she pees on me! Some just like to hold off when they're out and others aren't fussed either way.
The sniffing is fine too - my girls sniff more than usual when a storm is on its way so it could be even something in the weather. Like Wiebke said, smell is more important to guinea pigs than sight, so she's just working out what's around her so she can make sure she's safe