Note a quote in which Mrs.Bennet's reaction to Mr. Bingley's absence is revealed and use this as basis to characterize her.

I can't find a quote which she openly states this but here is a quote from Austen's narrative in Chapter 23,

"She hated having visitors in the house while her health was so indifferent, and lovers were of all people the most disagreeable. Such were the gentle murmurs of Mrs. Bennet, and they gave way only to the greater distress of Mr. Bingley's continued absence."

This reinforces Mrs. Bennet's only concern which is herself and her fortunes.