Frequent argument with mum

I am now married with 1 child. I am working, so my mum helps me to take care of my baby. I have a sister, whom I have not been talking to her for the past 4 years. My sister and I fought four years back and we still have the sour feelings in us. However, that does not bother me much as she is also married and living in another state. My problem now is, my mother likes my sister more because she lives far and they rarely meet. With this, they rarely have any argument as well. However, I see my mum daily as I need to visit my son who is growing up there. My mother does not irritate me or annoy me. She takes care of me and my son well. However, one of my close cousin told me that my mum is always been talking bad about me to her siblings. With this, her siblings get influenced by her and irritates me sometimes when i see them. Whenever she talks bad about me, I got to know that through my cousin. She tells me about it because she also feels that my mum is being biased and talking unnecessarily about me to others. This really saddens me and make me angry towards my mum. However, I cant ask her straight as I do not want to put my cousin in trouble. So, I keep it in me and talk to her as normal. However, I could feel that my mum is pretending to me and trying to save the relationship, as she doesnt like problems. But, I feel that our relationship is not through. If it is some other person, I would have avoided that person long time ago. Since she is my mum and taking care of my son, I cant avoid her. Sometimes, I just feel so betrayed by her and would indirectly show my anger to her. I also could feel that she is talking to me just for the sake of talking. I really do not know how to handle this relationship. I cant avoid her totally, at the same time I cant be in a fake relationship with her. This always ends up in argument between us for unnecessary things. Please help how can I handle this situation with my mum.

I cant say it fully as i do not want to put my cousin in trouble. But i have told her some of it. I want her to know that i know what she is talking behind me. I dont mind her saying anything to me directly, but not behind me. Afterall, she is my mum, and shouldnt be talking unnecessarily about her own daughter to other ppl. For me, to preserve a good relationship, u can talk anything straight to that person, but not ridiculing that person to other people. Regarding the money, i offered her many times. But, she didnt accept it. Regarding the house chores, i dont really do as i am also working and i also have my own house chores to be done daily after work. I dont have much time to help her. But, i dont mind helping her if she ask me out. She doesnt ask me out, but talking about this to other people. But, i always understand that taking care of a baby is not easy, and whenever i can i take him back. I wish i can give him to a baby sitter, but frankly i dont think i can find anyone who can takes care well of my baby. My mum takes care of him very well, i dont deny that. Even if there is anything she doesnt know or makes a mistake, i tell her nicely. I dont go around tell people that she doesnt know how to take care of him. I know how hurting that will be. I dont want to do the same thing what my mother is doing. I am not saying i am perfect or right. But, as a mother you should treat me like your own daughter (like how she sees her other children) and dont talk bad about me to other people. I asked her this. "How do you think my relationship with my husband will be, if there is any dissatisfaction, he doesnt tell me, about talk bad about me to other people. Do you think we'll live happily. That's what our relationship looks like now". Thanks for your feedback. Please do give me your opinion if you have anything else to say.