Awkward Xmas family lunch with horrible mother

I had another wonderfully awkward xmas at my parents again this year. I have always gotten along with my dad and speak to him atleast twice a week but it always has to be while my mum is out or at work as she gets seriously jealous. 3 weeks before xmas my dad called me up asking if i knew a good place to buy a dishwasher as theirs had died. I said yes and that if they wanted to come to my place i didnt mind driving them to the shop ( i live 45mins away from them). They came up and i took them around to the shop and they bought a dishwasher in their price bracket, everyone was happy. Dad mentioned the oven was on its way out and looked at pricing to this aswel, but decided not to purchase that day. Fast forward to xmas day, when we got to my parents for lunch dad dragged me into their back room to show me the oven unit he bought, which just so happened to be the one they where looking at when i went shopping with them. I said oh u found another one i hope you got a good deal. Then my mum pipped up and said oh yeah we went back to that place and bought the one we where looking at and then laughed. When i asked what was so funny she said oh you called your dad when we where buying it and you didnt even know we where around the corner from you. Dad then said i asked her if we should tell you and drop in but your mum said no, so i didnt. Both hubby and myself where stunned. My parents come to my house probably 5 times a year as they dont like to "travel" ie waste petrol to drive 45mins to my house. So to me i would think hey lets kill two birds with one stone and see our daughter and grandchildren while we are their as we are only 5mins away. While processing all this on xmas day my brothers and their partners asked what was so funny as my mum couldnt stop laughing and she told them and they all laughed aswell. I was so upset i had to walk away if i didnt i would have lost my cool and didnt think xmas day was the day to loose it. But It made myself and hubby really upset, one of my brothers still live at home and the other lives only 5mins away and they see each other all the time.

So now all day today i cant stop thinking about how much it hurt that my mum thought it was so funny, and it seems she thinks my reaction is even funnier. I really dont know how to handle this, i have never had a great relationship with my mum and seem to get along so so much better with my MIL. I dont think she should get away with treating me this way, and I really feel i should say something about it. I usually talk to my dad about her behaviour but i know he hardly ever passes things on because she never changes. How do i talk to my mum and explain to her that her actions really effect me and my family with out it blowing up in my face and becoming an all out war??