I feel weird

I babysit a 5 month old for my cousins. But I think the mother is starting to get a little jealous of me... I’m there almost 12 hrs with the baby during the day. I’m there when she wakes up( I’m watching her while the parents get ready for work) I’m the first one she sees and holds her in the morning. The mother does not hold her in the mornings. During the day I’m the one feeding her, I let her sleep in my arms even if that means holding her for 3 hrs. I get down in the floor and play with her. Her mother has said the baby isn’t “ happy to see her” in the evenings when I leave. I don’t want to ruin there bond but this is my full time job. Advice??