AIBU to think MIL's grief is a step too far?

[PandaEyes25]

Bit of a long one but please bear with!
2.5 years ago my MIL left FIL for another man. It turns out she had been having an affair with him for about 6 months (that we know of, I suspect it was longer).
Other man was diagnosed with terminal cancer a few years before she left FIL for him. Despite knowing that he had less that 18 months left, she moved out of the family home and set up on her own.
They split the week by living together partly at hers and partly at his home.
They were engaged less that a month after she left FIL.

I know I'm going to sound awful here but when he died she sort of went a bit OTT and grieved somewhat unaturally.
She postponed the funeral so that she could "spend more time with him" and visited the Chapel of Rest everyday for up to 6 hours at a time. This was at the height of summer and used to joke about when the staff told her they must "put him back in the freezer before he started to defrost".....
She moved all of his belongings from his house over to her small flat and hung up all his clothes in her wardrobe. She has refused to get rid of anything and now her flat is full of boxes( literally floor to ceiling). You can't sit on her sofa as it's got all of his books/ newspapers etc on it. She sits on a dining chair in the middle of the room infront of the TV as that's the only place that's free from the junk.
She has printed off photos of his body from after he died in hospital and has got them plastered all over the walls.
His son has asked for his ashes to be buried but she has denied him having any say in what happens to them. They are currently sitting on her bedside table as she "doesn't like to sleep alone".
She has now had part of his ashes made into earrings.
I know everyone grieves differently and that they should have the right to act/feel/do what they see fit but I feel like after 10 months it is not getting better and that she is wallowing in it.
She laughs about constantly turning up late for work and missing staff meetings because she struggles to leave the house in the mornings. I'm seriously concerned that she will start to jeopardise her job.
She also demands to meet us every weekend-sometimes twice. And then cries/strops if we say we are busy as she doesn't like to be alone.
DH agrees that her grief is unnatural but just thinks we should leave her to it. MIL and I have had a somewhat stressed relationship as of late but I am getting seriously concerned that she is on a downward spiral of self destruction.
Any advise would be highly appreciated!!

It doesn't sound like she is coping & should get some counselling. Even if it's to get her to understand his son has a right to grieve too and say goodbye

I understand what another poster said about the first year, everything felt so significant, the first Christmas, 1st birthday with out them, 1st Easter Sunday, because life had changed it would never be the same. Those 1st significant dates without them felt like a punch in the stomach & the grief was so raw. I was focused on those dates as a milestone of moving on. Time doesn't remove the pain, it just the shock of losing them lessens. I kept everything I could of my nan's only in the last year have I been able to let items I don't need go, it's been five years

It's difficult. She sounds very unwell and, tbh, doesn't sound like a sympathetic person. The will thing and the ashes situation sound terribly unpleasant.

I understand that you want to support her, but your DH wants to leave her to it...I'd be inclined to tell her she needs counselling, that's she's being horrible about the ashes and follow DH's lead.

It sounds like part of it is to punish your dad, to prove how much she loved the om, thus justifying her actions and showing everyone else how badly deprived she was. I'm not explaining that well.

I get what you mean jux. She's trying to show how distraught she is to prove how much she loved this other man, and by controlling all that he owns she is trying to prove how well she knows him and what he wants done. I get a glimpse of that too but don't want to judge as I can't see what this person is like.