You don't have to be a people pleaser...

So here's the deal, my boss is on vacation until October, my mom is working a whopping 12 hours a week, and the insurance agency is all in my hands. With two weeks of non stop rain and flooding the insurance agency I work for has been crazy busy. Not to mention all the day to day work. My mind is frazzled, my patience is thin, and I am having a hard time keeping up, and keeping policyholders happy. I worked two hours later than normal office hours last night just to return missed calls.
So my mom came in to work today, worked a whopping 3 hours and decided she was leaving. The phones have been ringing off the hook, and when I asked her why she wouldn't stay she said "it's Friday, I have a hair and nail appointment." Then she told me I don't always have to answer the phone, let the service get it and if I don't call these people back who cares? Well, I bet they care! She informed me that I don't have to be such a "people pleaser". but isn't that what I get paid to do? So now I'm feeling really underpaid, especially since she makes $3 an hour more than I do to sit on her butt and play Bejeweled, while putting everything on my desk.
I love my job, and I believe it is my job to do what I can to take care of the policyholders in this office. But I am so frustrated with my mom right now. Boss called in for payroll today and she told him she's been working 9-5, when in reality she's been here from 9-12, 3 days a week! So I said something to her about it, and she laughed me off. Told me to stop being such an overachiever.
I thought customer service became lousy with my generation, am I wrong in thinking maybe the seed was planted in my mom's generation? Phone's ringing, gotta go people please...