Hatred Towards Inlaws

Over 15 years of married life, I have hate feelings towards mil and sil.
Mil being a parent , I still give her the credit and let my husband spends money his time etc on them . I do not get upset with that though I do not trust her at all .

With sil, I do not want to spend my hard earned money for no reason. I dnt want to give her gifts when she cannot even respect me and treat me like a person. She never calls me , lies to me , hide from me and in front of her brother try to be super nice to me . I can see all this and have started to stay away and talk to her with husband only .

but my husband is always giving her lavish gifts : to her and her kid . We have kids too : she never sends my kids any bday gift just one small gift during the entire year during Christmas . But My husband sends her or her son something after every 1-2 month. I just hates it . Also he makes sure to send her the best of best things rather than just giving anything simple .
im not able to make peace with this arrangement. Whenever I have told him that she doesn’t do anything then what is the need , he just get angry and feel that he is supposed to do it . This all is because of my mil telling him all the time as how he is suppose to do for his sister .

how do I make peace with this. I feel very angry for sending her gifts because I could have used to that money to buy something extra for myself . After all it’s our hard earned money. I could buy something Extra for kids . I slog myself so much with housework here , I could use that money for hiring house help for extra 1-2 days

on the other side : My mom says just let it go and think you ares doing some seva
But then why can’t he do the Seva for my family ??? Why is the seva always for his family ..
some people will say you also send it your house and siblings . But that’s not the solution that’s a revenge.
I dnt want to send it to my sil an lavish her for being a sister .. she is grown up working women now , she need to act mature now . We have kids now . We are all suppose to spoil kids now and her age of being spoiled is gone ..

 

He gives at least 10 times more to his parents and even sister . So if he sends his sister a $100 gift then only $10 to my sister
Just as an example and I’m done with this nonsense now