Don't forget, Sir William Lucas has a "large party" assembled in Ch. 6, and Jane always meets Mr. Bingley in "large mixed parties."

This rather implies that either 'large parties' were the norm, or that they depend on circumstances: a large party brought to a public ball might mean 'more than usually arrive together,' whereas a 'large party' at Sir William's might mean 'large for a drawing room his size.' So, Jane might not be invited to every event Mr. Bingley was, but if the party were large enough to include the principal families, she and Bingley would both be there.