It was only after this incident when I apologised and explained...that I was wondering why we had very clearly been left out and tried to explain in one sentence that my childhood issues make me insecure, that I got a torrent of abuse back saying she doesn't care, she isn't interested, she has her life to live. The rest are 'ok' with me
Its good that the rest are OK with you, build on that. It sounds like a difficult situation and without being a fly on the wall we can't know exactly how to deal with it
But...
It does sound like a lot more went on between the two of you than is in the post, apologising, explaining etc..
Its not a good idea to say things like this;
tried to explain in one sentence that my childhood issues make me insecure to a woman who clearly doesn't like you... because lots of people have problems in their lives, so you are not the only one, although it may feel like it. At one time in our school, various parents were dealing with bereavement, infidelity, financial problems, serious illness, redundancy - and in general the rest of us just didn't know at the time.
Also, , she doesn't have to like you, and you don't have to like her. It would be nice if you both did, but she's clearly made her mind up. . Saying stuff like that to her is just inviting her to have another go , which it seems she did.
Your daughter was excluded by this person, but perhaps she knows you've called her DD the class queen bee and your tone when talking about them is quite aggressive. How do you expect them to react to that? Is that more likely to make them include your DD or to plan things without her so that they don't have to deal with you?
Think about what the best end goal is here. Was it to tell this woman off, which may be satisfying but is short term but doesn't improve the situation or whether it was to improve things for your daughter? If it was the latter, Is there a better way that you could have handled this?
Honestly the BEST THING you can do for your DD at the moment is to stop talking to everyone about all of this at school. Do not engage with this woman again, try to keep things civil, as in don't make a big show of ignoring her, but generally just keep away from her.
You say the rest of the group are OK with you, but don't expect them to want to get involved in this argument at all and so do not discuss it with any of them. At all. If you talk about this other girl and her mum in the way you describe them here, it will not go down well. I promise you. Generally people don't want to be dragged into the problems and dramas of people they don't really know that well. Its only going to carry on the issue, make them back off and worry about getting too involved with your and your DD and provide more drama and problems for your DD.
It sounds like your DD is able to make friends, so step back and give her a chance to do so.
She has several years of primary school ahead of her and there will be many occasions where you think things are unfair or should be different. You need to approach all of this more calmly.