Allsorts
When you are estranged you cannot believe it, so unexpected for lots of people. It’s helpful talking to people who understand, we all have different reasons for it happening . I would only ever advise anyone to stand back a little, don’t force discussion if they have said they don’t want it, but say when they are ready you want to put things right and listen to what they say. There are mil’s and dil’s who are from hell. Hopefully most estrangements resolve, but if it doesn’t we have to learn to live with it. What you don’t want is people thinking they know what they think you did wrong that enabled estrangement , it’s not one size fits all. it just hurts.
Estrangements aren't one size fits all--very true statement. This is precisely why the constant hypothetical references to the DIL being coercive or controlling is so negative and divisive. There's no proof. In fact, the DIL's distance from the OP is the most rational part of this whole thing. There is no healing purpose behind trying to drive an evidence-lacking perspective into this specific situation. The end result of the OP fashioning her DIL as the problem will be estrangement. It will not bring her son closer to her, but further away. It's a hypothetical that is strictly meant to divide.
Taking a step back, not continuously broaching the subject that clearly enrages her son, it the best way forward. If he gets angry at the discussion, leave it be for a while. MIL, son, and DIL all seem to be hurt by each other's behavior. A step back can do wonders here.