Mrs. Nguyen is the owner of the nail salon, Day Spa and Nail, in which Jimmy McGill's office is located.
After hearing it from her cousin, Mrs. Nguyen starts complaining to Jimmy for agreeing to represent three teenage necrophiliac boys, then orders him not to drink the cucumber water that she offers to customers only. ("Uno")
Mrs. Nguyen informs Jimmy that he has a customer waiting for him inside the salon. ("Mijo")
Mrs. Nguyen gives Jimmy a suggestion for which color to dye his hair. Jimmy likes his choice of color better and tells her that he will just wash it out the following day. Mrs. Nguyen tells him that it doesn't wash out and he quickly changes his mind, telling her to simply style his hair instead of dyeing it. ("Hero")
Mrs. Nguyen again chides Jimmy when he goes to drink cucumber water, exclaiming that it is for customers only. Going by his new "done doing the right thing" mentality, he defiantly drinks the water straight from the spigot. ("Switch")
Jimmy returns later to pick up his Davis & Main company car from the nail salon as the workers huddle around the car in awe and Mrs. Nguyen watches from the doorway. Before he departs, he jokingly asks if Mrs. Nguyen is going to give him a hug goodbye as she shakes her head and walks back inside. ("Cobbler")
Mrs. Nguyen asks Jimmy why he is back sleeping in his office at the nail salon. Jimmy tells her that he has the place paid off, so he is allowed to come and go whenever he wants. When Jimmy smells coffee, he gets Mrs. Nguyen to fill up his cup by telling her that the sooner he gets the coffee, the sooner he'll leave. ("Bali Ha'i")