I have 2 DSC and 2 shared DC with my DP. DSC live with us full time. DSC see their mum sporadically. Over the last few years it has been increasingly obvious that my MIL favours DSC over our shared DC. She constantly buys them gifts, gives them money and new clothes, takes them on days out and has them for sleepovers yet she never ever does any of this for my DC. On more than one occasion she has given money or new clothes to DSC in front of my DC who are now starting to become old enough to understand that they aren't getting anything whilst their older siblings do (previously they were too young to understand). This has obviously been a huge bone of contention and DP has raised it with her a number of times.
Last weekend, yet again she took DSC for a sleepover and day out which DC were not invited to. They then came home with so much stuff, new toys, clothes, bedding, posters, shoes. I was so angry that I had to leave the house with DC before I got into an argument with her in front of them. DP was furious also and told her so and that she was not to buy DSC any more stuff if she is not going to treat her grandchildren fairly.
The last night oldest DSC13 was on the phone to her in the next room from me and had left the door open. He had her on speakerphone. I was sitting online ordering something and wasn't intentionally eavesdropping but I could hear every word. She told DSC that she was on the cusp of falling out with his dad because he was saying that she should not be buying things for DSC and not DC. She told DSC13 that she was not happy about this and that she 'won't be playing that game'. She then said that she loves DC but not like DSC and that it's different for them and then went on to make an arsey comment about my family. At this point I walked through to the doorway of the room that DSC13 was in and said, "MIL, just to make you aware, DSC13 has you on speakerphone and I can hear every word that you are saying" and walked away. I was so angry I was shaking.
DP wasn't in but I phoned and told him immediately and he was equally as furious. However he is really ill at the moment with the flu and said that he wants to wait until he has a clear head before he speaks to her. In my mind there is nothing to speak about and I don't want her to be any part of my DC's life if they are going to grow up being visibly rejected by their grandmother. I understand that it is shit for my DSC that they are not growing up with their mother consistently in their life and she may feel the need to try to make up for that but as far as I am concerned, you don't fix an imbalance by creating another imbalance and my DC is completely innocent and does not deserve to be treated as lesser.
I drafted a message which I was going to send to her basically saying that she will no longer be able to be a part of DC's life for the near future, until I have decided what is best for them, she is not welcome in my home and should she wish to buy anything for DSC then she can do so and keep them at her own house. I was then going to block her and move on.
I have spoken to my family who are absolutely disgusted but are telling me not to send the message and to give it some time. I feel like my family are often overly forgiving of people and this is not something that I want to move on from. Recently I have started to notice DC trying to get attention from MIL and I am worried that she will grow up trying to get love from people who don't put her first or willingly give it to her and I worry it would impact future relationships so I think the best thing would be to stop contact altogether. AIBU? Is there anything else I can do?