Mil and babysitting

I'm afraid that my baby will love my mil more and just the idea makes me mad. My baby is 1 month and I'm debating whether to go back to school and work this semester or wait until fall. The reason I'm hesistant is because mil would be the one who takes care of him. She is always saying oh he loves me the most, and I love him the most, he is going to call me mimi and I'm going to take care of him all the time. She is a retired lvn nurse so she thinks she knows everything. But everything she knows is outdated, she insists that baby should be on their side, and to prop with pillows etc. I am constantly telling her how I want to raise my son and she is always arguing against me and when she babysits him I'm afraid she ignores what I say. If my son is around her a lot he will prefer her. Okay rant over.