There are so many things we don't know about this situation.

How well-trained is this fiddler? How good is her instrument? Is she actually hearing the guitar as it sounds, or is she registering some distortion caused by the sound system or the room you are in?

How long have you been playing happily with others? How long has SHE been playing happily with others? That should tell you something.

Frankly, given how hard it is to play violin, I suspect the problem lies with her, not with you, Texas Guest. Best of luck.