The Ethereal plane is a foggy, grey plane that deadens the senses. I doubt she'd be able to see anything clearly at great distances, but she might see the spires of a city poking out of the fog occasionally once she got within a mile or so of it. If she gets more than 60 feet from her party mates, she might very well lose contact entirely with them, as that's as far as he can see into the Material Plane, IIRC.
Yes, anything that can see invisible creatures can see ethereal creatures as well. In addition, there are ghosts on the ethereal plane, which could in theory be helpful to her, but are more likely not to be. There are also creatures that prey on material creatures there, like
ethereal filchers and
marauders. Since those are in fact intelligent and neutral, she might be able to convince one to help her find a way back to the material. Being natives of the ethereal, they might be familiar enough with it to actually know a way back.
The filcher/marauder/ghost could certainly jump back and forth to the Material to act as a messenger to her friends as well, so she could be less isolated and they could all work together towards getting her back. Maybe the filcher/marauder knows of a nearby hedge wizard who might return her to the Material in exchange for some service from the PCs.
There are a lot of directions to go with this. It sounds a lot more like a opportunity for some fun than anything.