My 100 year old mother constantly scratches her nose when I feed her. Does this mean anything? She has dementia, but not Alzheimer's.

TerriLK, sounds like a nervous tic of some type. Sorta like people who twirl their hair with their fingers when they are nervous.  Maybe she did that type of scratching when she was a child.

Since your Mom is 100 years old, my gosh imagine all the changes she has seen in her lifetime, I wouldn't about it unless she is damaging her nose when she scratches.

She eats a normal diet, no difficulty swallowing. It just drives me crazy because I'm trying to feed her and she will move my hand out of the way to scratch her nose. It's just frustrating. Must just be a tic or something.

Is she eating a normal diet? Have you noticed any problems swallowing?
It's really hard to guess what might be going on based on your question, she could be trying to push the food away, or a dysfunctional swallow could be forcing food and liquids up her nose, or it could just be a tic. Is it really a problem or are you just wondering why? Does she fight if you hold her hand to keep it from happening?