As they get older the numbers you can have to parties often get smaller...easier when you can have a village hall/bouncy castle to have 30 than when it's a specific activity. So best to prepare your DD for this sort of disappointment.
A few things have stopped us inviting other children to parties/playdates. The main one being meanness/unkindness/perceived unkindness (e.g. "Bob laughed when I got a question wrong in class today"). If my DCs are coming home complaining about another child then, if a decision has to be made about numbers, Bob won't make the cut.
In that age children, I've also come across a bit of the super-confident children (girls) pre-empting the guest list and being manipulative "I am going to be invited to your party, aren't I? I'm going to buy you the BEST present ever!" (yes, I've witnessed that).
Maybe they are trying to reciprocate invites their DC has had?
And yes, there are the parents who are cliquey and look down their nose at you. We have one of these (mums) in our lives and I think my DC would have to win the lottery, cure cancer and then turn water into wine in front of her before she'd deign to extend an invite to either a play date, let alone a party (for the record, DC is a lovely kid, very popular, very kind and gentle and doesn't have any SEN - my other DC does, so I know that one as well).