Step #1 is they have to post a picture of themselves on AT and get a lot of attention from guys here. They should start talking to one in particular a lot, hopefully someone who is almost 30 and lives in their sister's basement so they have something in common. Get them drunk and have them message about "adult" topics to this person.
Step #2 is to have them stop talking to you pretty much. They should make conversations short and stop saying "I love you" and such in messages. You should notice this change and try to give them space. You should assume that they just need some time and not push the matter.
Step #3 is that they will perform a social experiment on you and wait to see if you will initiate conversation on the topic and actively try to fix the problems you haven't mentioned. Don't worry, just keep giving her space and things will be over soon.
Step #4 is that they will send you an e-mail explaining that they think things are over and that you need to talk.
Step #5 is to come home and talk about things that are actually really over but you don't know it yet. Don't worry, it's not you, it's them. They need their space. They haven't been on their own for almost 5 years and they need to find themselves.
Step #6 is to talk about second chances and how you didn't know what was wrong and really want things to change for the better. You'll be willing to do anything to make things work and are really shocked that it's ending so soon and without warning.
Step #7 is that they will agree to stay and work things out. You get really excited, but don't worry... it wont last long. They will again change their mind and want to leave.
Step #8 is that for about a month you will live an awkward existance as they look for a new place to live while still sitting next to you all the time as you think about them.
That's how you do it.