First off....not wrong, wrong, wrong. All six of the kids in our house coslept with their parents. They are all now in their own beds. They moved on somewhere between ages 2 and 8. You haven't done anything wrong. You're just ready for a change a bit before she is. This is okay.
Ideas:
Go at it gradually in space. Start her on the floor of your room. A folded-up pile of blankets will do for a bed, if there's no room for an additional mattress. Let her spend a month or so on the floor of your bedroom. Then move her to the hallway outside your room with an open door, then in the hallway with a closed door and just slowly creep her over to her own room.
Go at it gradually in time. She must start in her own bed, but can join you in 1 hour. Then 2 hours. Then 3 hours. Slowly expand the time until she's in her bed all night. You can get clocks for kids that change color at a certain time. This lets her check if it's time to join mommy yet, but won't wake her up if she's asleep.
Go at it gradually in days. She must sleep in her own bed on Tuesday nights. All other nights she can be with mommy. Expand it to two days, then three, etc., etc.
Combined with any of these approaches:
1. Lots of snuggles during the day and especially before bedtime.
2. Lots of rewards, attention, and praise for sticking to the rule of the day/month. Brag on her to your friends in her presence (make sure these friends know to be supportive and not nasty.) Praise her courage. A sticker chart might be helpful. Remember that the best rewards will probably be special time with you. Spending a night in your bed might actually be a great reward.
3. The best penalties might be withholding attention. For example: "oh, you came into my bed last night, so I didn't get enough sleep. I'm too tired to play a game with you. I'm sorry." This would be a natural consequence.
Check out Elizabeth Pantley's "No-Cry Sleep solution" series for ideas as well. Among other things, she's got a protocol for a stay-in-your-bed fairy that leaves small gifts for kids who stay in their beds.
When she's done a good job staying in her own bed, it is perfectly okay to welcome her into your bed for special snuggles on special occasions: feeling sick, birthdays, etc. You can also use a night in mommy's bed as a reward for staying in her own bed. For example, if she can do a whole week in her own bed without crying or complaining, she can have one night in your bed.
Good luck.