Should i continue to help and give to my wifes sister?

My sister n law and i have not been on good terms she has stolen from us used us, ruined some holidays, said some bad things and uses drugs. All in the first 3 years of me being around her, as of this year she has tried to be more respectful and has apologize. I still don't agree with her lifestyle and the choices she makes and has never once done anything to help us or given any kind of gift to us or our kids but my wife is fighting so hard to buy her things and give her gifts and i don't want to, so am i being a jerk or should i give in and put smile and let it go.