My Mother Is 85 .Her Temp. Is 102.9. This Is

My mother is 85 .Her temp. is 102.9. This is the third day her temp. has risen toward evening. Her temp. was normal @ 1 when I got home from work. She doesn't seem to have any other symptoms . She is just very tired and I had to talk her in to eating as she said she wasn't hungry. Are these symptoms serious enough to go to the ER or should I monitor her to see if she gets worse.