If your DM's life of retirement feels the same as lockdown then I think you need to cut her some slack because her life must be awful.
You have no idea how she felt when she retired, so while you think she's dismissing your feelings, you're doing exactly the same with her feelings.
I'm retired and I live alone, apart from the dog, and I can assure you my normal life is nothing like lockdown, if it were I think I would have sunk into a deep depression by now.
I do not normally spend my life trying to find things to fill up my hours because I've got nowhere to go, other than to walk the dog, as I do at the moment. I can go out and see people, do things, get on with my life.
I'm hating lockdown and at the moment, I'm finding it hard to motivate myself to do things like DIY in the house. I feel stuck and bored.
If your DM feels her life is like that because she's retired then I feel very sorry for her.
No one spends their working life gearing up towards retirement. When you retire, for a great many people it's a huge change, and can often cause loneliness and depression.
I'm close with my family, in contact frequently, but I have no in my home with me. I haven't touched another human being for weeks. I can't hug my children or grandchildren.
A great many people are finding lockdown hard, both retired people and working people, just because someone is retired and used to being out of the work place and alone doesn't mean it's easy for them; life isn't just about work and the work place.
Different people cope, or don't cope, in different ways. It's not a competition as to who has it harder.