I have the same problem with BOTH my boys, i have them in daycare one day a week for my own peace of mind (zhai goes 2 days) and a day to relax and unwind. It sounds bad but sometimes i just need a little timeout. I also put them in to learn that im not the only person who can care for them, and it seems to be working for jett. Zhai is used to it now, and loves going to preschool (has been for 1.5 years) Jett loves it now, when we go to drop Zhai off on wednesdays Jett cracks a wobbly to go and play...
Sorry got off the subject there a little...
When Jett is really clingy i dont pick him up i sit on the floor with him for 2-5 mins and play then get up and do what i was doing... It works for me sometimes, other times i just have to let DF/FSIL listen to the crying and walk out for a bit. Maybe drop her off at your mums for a while??

Hope that helps a little..