Shannon is the friend of Gru's pesky and irritating neighbor Jillian, who has set her up on a date with Gru (against his wishes, and much to his dismay). 

Shannon is a narcissistic, materialistic, rude, selfish and dim-witted young woman who is all about being a slave to trend, though she is also into exercise and sports.  She spends an inordinate amount of time on her smart phone, and chewing gum.

After Gru gets suckered into a date with Shannon, things start to unravel very quickly, until the unexpected but timely arrival of Lucy Wilde, who tranquilizes Shannon just as she's about to have a meltdown on Gru for wearing a toupee on the date with her (she "hates fake people").  Lucy and Gru then spirit her out of the restaurant, tie her on top of Lucy's car, and drop her off at her home while she's still tranquilized.