Hope you're okay Lulu
What sorts of things set her off in the morning?
How does she keep her bedroom? Is she organised? This can often have an impact on her mood etc.
Have you tried things like laying her uniform out the night before so it's all ready for when she gets up? Let her choose her underwear, socks/tights and what she wants in her hair e.g. clips, hairbands etc. She could have then all layed out on her drawers/chair/desk etc so when she gets up she can put them on.
Also, make sure she has everything ready for school the night before so things are not rushed in the morning. Try and make the morning as relaxing as possible.
Does she have a routine? If she doesn't have one at the moment, maybe set up a regular routine so she knows what to expect in the mornings.
How about some of these:
Spending some time with her everyday after school doing a little activity she enjoys e.g. colouring, playdough, barbies, playing the garden - anything that she enjoys that you could do together.
Before she goes to bed, talk about all the nice things she has done that day. Having a positive frame of mind before going to bed helps sleep and helps children wake up feeling happier.
Hope some of these have helped, if you want any more suggestions, am more than happy to help. Let me know how it goes