I can't tell from the picture but it sort of looks like a bit of the tissue around her eye is swollen, like maybe something got between her eye and eyelid and poked? Or maybe an infection? It's big enough that I would think if it were just a piece of fabric or something that she would have blinked it out by now. My instinct on this would be to go to the vet, if it's a poking injury or something stuck in there they would probably be able to flush it out, and if it's an infection it's always better to get it handled sooner rather than later. That said I'm a new piggie owner so I could be over reacting. Hope she gets well soon!