long distance crush
The kinda mental illness that rips you apart from the inside. 'Tis an idiot that develops one, and yet anyone can fall prey.

Either you move on, or wait until you can see each other on a regular basis to go beyond friendship, or confess and renew all agony no matter what their answer. If they like you back, the distance will kill, and if they don't, then you just screwed up a decent friendship, sucker! It's a salope of a situation.
doctor: And what are her symptoms?

concerned individual: General moodiness, addiction to her phone/computer, inability to keep from mentioning a certain person on a regular basis...

doctor: Has this lasted over a month?

concerned individual: Well over.

doctor: We have here a severe case of long distance crush. Behead her and end her misery.