DD wants to exclude one girl from her bday party

Honestly, if this girl is in the regular friendship group that (for example) eats lunch and walks home together every day, then dd is being a bit unkind to single her out and invite the rest of the group but not her.
I suspect what Op means is that the girl hangs around with this group but is not particularly close to anybody in it?
That being the case, being excluded could be a shock and quite hurtful for the other girl and I’d encourage dd to think carefully about the impact and have a little empathy for her.
Will she actually spoil the party for dd in some way EG bossy/domineering, makes nasty comments to people?
this would be a factor too.

Which is it? Does she not have friends or is she in the same friendship group?

Friendships at this age are very fickle and in a few months this situation could be very different and your dd could be the one excluded by one of the others. As a teacher I have seen it play out countless times. If your dd and this girl are in the same friendship group and hang out in this group, it is simply mean to not invite her.

How old is your daughter? If it's was the only girl in the class at primary school I'd say you probably have to invite her but at secondary school, I think that's when they all branch off and form different friendship groups. If this girl isn't one of her friends then she doesn't need to invite her.

Yes this, Is what I was getting at.

Is unclear what you mean by "this girl doesn’t really have any friends and DD will also be inviting everyone else from her friendship group".
Either the girl doesn't have friends so she isn't in the group nor excluded, or the girl is in the friendship group so she absolutely has friends. Appreciate you're muddying the waters a bit to make your own DD sound good, but it affects the answer. In the first case it's fine and even best to leave her out; if she doesn't have friends then that's something she an her own parents need to work on more generally. In the second case, your DD risks everyone else dropping her for being nasty to this girl. You know which it is, so make sure you think over with DD the possible ramifications.

I agree let her invite who she likes. It's not like a class party where she's leaving once person out.

She should choose who she wants and be prepared to face any repercussions. It's also a good opportunities to use some empathy and think about how she would feel in that girls position

Let your daughter exclude her if she wants. The girl she excludes would need it too. It's horrible to be strung along when someone doesn't like you. The excluded girl may end up feeling relieved that there was an end to all the pretence - and either way she'll get over it.

She's old enough to make her own decisions. I only intervene if my children have been invited and attended someone's party the same year- then they have to invite (unless huge fall out).

Why is she hanging out with this girl if she doesn’t like her?

Do they still hang about together? If not then it is fine not to invite her, if they are still are in the friendship group it is more awkward to negotiate and leave her out.

I would leave the decision entirely to DD.
She's old enough to choose her friends and if the previous friendship made her unhappy, that's reason enough to exclude her.

At that age it's up to her imo, they aren't little kids anymore

If she's managing the friendship now while still in a group with her, then what would be different about managing the friendship within a party context? Sounds like they've got a new balance day to day.
Absolutely would not exclude one from a whole group. It's damaging and I would never let my child do this to someone in a "friendship" group.

Honestly, at this age I would say DD invites who she wants but needs to be prepared for awkwardness and a difficult conversation. Her birthday party is about her, not pleasing others.