[quote=@chukklehed]
Aiden might invite her anyway, but if he doesn't she would definitely wonder what the only two other Dragon Slayers are doing leaving the guild when everything exciting is happening there.
[/quote]

Aiden would if it was a regular mission, as he's curious to see her strength, but this is their super important S-class mission that they think was given specifically to them to help prove their ability to become S-class mages. They'd want to complete this on their own and thus wouldn't ask anyone for help, it would be a slight against their pride as Dragon slayers.