DD1 (3.3) has always been on the clingy side, doesn't like me leaving her at friends etc. In saying that, I've seen a huge improvement in the last few months. She started nursery 3 months ago and took to it instantly , never got upset when I dropped her off and was always excited to go. She also goes to a couple of 'classes' a week which I wait with her at and she joins in the class enthusiastically.
Over the last 2/3 weeks however, she's getting upset about going to nursery and not wanting me to leave. Her key worker is having to take her off me (she's fine once she key worker has her). Also at her classes, she's not wanting to join in and just wanting to wait with me. If the instructor comes and takes her hand and gives her a 'job' to do she'll sometimes go.
It's frustrating as I thought we had really turned a corner. She's also getting upset when I leave the house, she LOVES her granny and sees her almost every day but Yesterday when I tried to leave to take DD2 to the doctors (Granny was waiting with DD1) she was screaming that she didn't want me to leave, she wanted to come with me etc 
I'm reassuring her as much as possible, she's a very cuddly affectionate child and has been requesting more cuddles which is fine, I'm just not sure why the sudden change in behaviour.m?
Any tips?