He will regret it big time if he tries to reinstate contact; that is the whole point of this exercise. You cannot support him in that respect, you stick to your boundary of no contact with his mother.
Its a response that she wants and you must not give this to her, she will know she truly has you then.
Do not acknowledge these items in any way shape or form. Dispose of these items via a charity shop and do not give them any more power. Radio silence from the two of you must be maintained. She wants a response from you; do not give her that satisfaction.
This behaviour is called hoovering. Many disordered of thinking people like narcissists use such behaviours to try and draw their chosen victims back into their dysfunctional web. Presents in such circumstances are used by such people to try and both manipulate and control. Its not caring behaviour in any way or form. She does not want to talk and or apologise; such people never apologise nor accept any responsibility for their actions. The rulebook of familial relations goes out the window completely when it comes to dysfunctional families like your DPs family of origin.
Do not fall for it, she has not changed an iota. Such people really do not apologise nor accept any responsibility for their actions.
Inform your DP of this as well. It’s not being abusive to another person to limit contact or interaction with them when and if they have proven themselves to be untrustworthy, narcissistic, sociopathic or vainglorious. It’s the moral choice to shun or avoid any person in a local community who has proven themselves to be abusive, neglectful, Machiavellian, or dishonest.