3 year old has a imaginary friend that won't leave?

My 3 year old daughter has this friend "izzy" for about 2 months and now she is getting Maggie into trouble. I have told her if izzy is getting her in trouble then she needs to go home and not come back. I understand it is normal for kids to have imaginary friends I had one but mine never got me into any trouble. Izzy will tell Maggie to walk down to road or go to the highway or hit her brother. Maggie is very loved and talked to but since her friend has came she is getting withdrawal from regular actives and eating the few say it's just a phase and she will out grow it but how long can I expect it