Being friends with her is not ignoring her feelings since she wants to be friends. He can still find someone else while maintaining a friendship with his co worker. I just said that if he stays friends with her there is always a possibility that she could catch feelings too.
For that to happen / be of any use for OP then he would need to remain available on the chances that she changes her mind, unless he is going to get with someone in the mean time and then drop that person when this first girl decides to see what OP has to offer, but yeah in the mean time he is sat blasting rope to her facebook timeline holiday pics from 3 years ago! >.> I hear people do that... honest!
Fancy hearing me on an amateur podcast with friends gushing over one of my favourite games? https://youtu.be/1I7JfMMxhf8