I recently had the same "silent treatment" you talked about. Initially it started from a small issue we could have easily talked through in an adult-adult conversation. She said she needed the time to think, and not ready to talk about it.

I was naive enough to continue contact her every day through text, talk to her like usual, asking if she's ready to talk etc. doing all that i can to get her back to talking, how miserably i've failed after more than a month of waiting. She was noncommittal but promised to call/see me on various occasions which none eventuated.

Just past weekend it lead to she asked me to move on and seeing others, pretty much its over.

This is extremely hurtful to see someone you shared so much with over a long time could be doing this to you. Either its through immaturity or they are seeking a way out but can't face you to talk about it in person.

I should have posted my issue as ask for direction from earlier on. Looking back what i (and yourself) should best do is to cut all form of communication, give her/him the time/space they say they need, if they come back, work out what wasn't working then.

Also do not talk about emotions like Bouffy mentioned, do not pester/nagging like I inadvertently did in the hope of bringing her back.

Like everyone else said, it is definitely immature, melodramatic, manipulative, passive/aggressive style of communication and uncalled for in a healthy relationship.