My dog doesnt like my Mother anymore/could he sense somethin

[Beautiful Border Collie]

Casey used to love to see "Grandma". He would run in her house and jump on her lap. I always had to tell him to get down. He would always sneek a paw up on her lap though.BUT- For about 4 months now, he wont go near her. He will jump over the love seat so he doesnt have to walk in front of her. When i say "go see Grandma", he will jump up on my lap and put his head on my shoulder. I hope he cant sense that maybe she has something wrong with her. I know some dogs can sense cancer. My Mother is in her 70s. She moved last August but Casey just started doing this in January. It really worries me that she could be sick and i dont know it. Has anybody heard of anything like this? She always gives him treats when i take him there. He eats the treats but still wont go near her. Its really sad. I feel bad for my Mother. She used to babysit him when he was a pup nearly 6 years ago.
He doesnt do this to anybody else and she has never hurt him.
Help me figure out whats going on here. :(

[Queen Bitch]

It's a possibility. There is another member here who had a dog with cancer, and her other dogs wouldn't go near it, though they had previously been a close pack. Have her go get checked out.

[imported_Kat]

Agreed. Dogs can sense chemical signals and imbalances which can upset their behaviour. If even to put your own mind at risk perhaps suggest to her that she could go for a check-up?

[Beautiful Border Collie]

She does have a black spot on her forehead. Hopefully its just my dog and not something wrong with her.

[courtnek]

she needs to see a doctor. ASAP. PLEASE!!