Your poor daughter.
What she has and is enduring is dreadful.
It maybe your writing style but it comes across as if you have been somewhat passive. Perhaps I am mistaken?
Having girls myself I would take this very seriously.
This is very very serious and will undoubtedly have a long term affect on her, despite what she tells you.
You need to formalise what your daughter has gone through by email to the school, as they sound very very poor.
In your place if she is still keen to attend the same secondary school as the bully and her friends, you absolutely need to act now.
Contact the secondary school Principal to put them fimly in the loop.
Copy the Head on what you have emailed the HT in primary.
Formally request that your daughter is put in a different class, and specifically mention one or two names of girls that she gets on well with to hopefully be put in a similar class, if they would be agreeable to that.
Double check with the other parents of girls she likes.
Doing the above will help your daughter to settle in and make a new grouping.
I would also organise a couple of counselling sessions, a safe place for her to speak.
She sounds like a great girl but she is likely protecting your feelings in all of this.
By speaking to someone unconnected and independent of her family, she can lean into how she feels, process her emotions and arm herself for her new school feeling more confident in herself.
It will be money well spent.
Doing this online with the right person is a very effective medium too.
Wishing you both well.