It's incredibly hard to make these decisions. I am clinically vulnerable, but was not shielding. I am very worried about the implications of my son going back to school. He's older though, and really wants to go back (if he didn't want to go I might make a different decision).
I think there's a few things to consider.
What are her thoughts on school, does she want to go?
Legally, she doesn't have to start school until the term after she's 5, so you could keep her off for a bit and see what happens (but you would need to discuss this with the school).
Have you spoken to the school about what measures they are taking, are you happy with them, is there anything that they could easily improve? Eg could they agree to let you know when there is a confirmed case in her bubble or in the school do you could take her straight out? Are they doing temperature checks? Etc.
What are the levels like in your area? It makes a difference if they are really low as to whether you feel the risk is reasonable. We've said if infections go over 20 in 100,000 (level that government use to determine quarantine for people travelling from abroad) we will take extra precautions (stop out of school activities for example), you could use something like this as a risk assessment guide for sending to school though.
What are the living arrangements like at home, how easy is it for your DD to socially distance from your relatives, can DD use a separate bathroom to your shielding relatives etc.
If you keep her off, what's the plan for her education? It would maybe be worth joining some home ed groups to get an idea of how others do it, find out the curriculum, especially for English and maths as they are the foundation for so much else.
I think there's lots of people in this position and it's awful. I wish you lots of luck whatever you decide.