mention anywhere that Emma may have snubbed the Coles'.

I think its Mr Woodhouse who is the person to be considered for an invitation and not Emma.
The Coles will have 'him' in their heads when thinking of any such step.
Refusing to invite the first gentleman of the town on the basis of the daughter's behaviour is hardly the right course.

Even Mr Elton excused himself to Mr Woodhouse before going to Bath the next day of the proposal as a matter of propriety regardless of his daughter.

They being first family of Highbury perhaps made them hesitate.

Emma is hardly ever out of Hartfield to have had enough opportunity of meeting and snubbing people and treating them badly.