I had the same experience with mine before. He was paper trained and all in the sudden, he started potty everywhere he wanted.
Try to limit the places where your little one has access to. Try not to yell at her because she'll think you're playing with her. When you see her sniffing around like she's going to pee/poop, pick her up and put her on the paper. Always have treats ready to praise her.
We always praise Sandy when he goes potty on the pad. Every morning when he's out of his bed, he'll walk to his pad and pee. After his breakfast, he'll go there for #2.
I personally think it's not hard to potty train them, it does require some time and patience.
Good luck
