Just friends

Someone I know (male) was talking to this female who lived in a whole other state pretty frequently. Like everyday. They had met once before in person a couple years ago. Anyways they both have similar interests and they have been talking on a platonic level for the past 3 months through Instagram and text. My male friend ended up expressing feelings for her and inquired about having a long distance relationship. The girl basically said that she doesn’t do long distance and felt it was best that they distance each from other for a little while.

Well my friend still wants to be friends with her, but I’m sure his feelings for her are still lingering. She’s basically distancing herself because she said it would be unfair for him if they continued at the rate that they were going. My question is, do you think that it is fair to continue a friendship after someone expresses feelings? Can that ruin a friendship? I feel like those feelings don’t just go away.