I have a boarder collie(1 year) who suddenly has gone off her food. She eats 1 meal every other day. Also I have noticed she is rubbing her nose a lot. Apart from this she is great.

Chances are, she needs to see a vet. See https://www.askmehelpdesk.com/dogs/information-articles-our-dogs-expert-labman-53153.html#post254171