Gift for terminally ill mother-in-law

I'm hoping you all can help with gift suggestions /advice for my MIL. It's her birthday (47) in 2 weeks plus mothers day and we have no idea what to get her.
She was diagnosed with terminal pancreatic cancer this time last year and wasn't expected to live 6 months. She's responded well to chemotherapy and is still doing ok and probably will be here for another 3-6 months yet, chemotherapy side effects are taking their toll and is now not being too effective.
We brought her a necklace with her kids names engraved in it for Christmas, thinking that would be the last gift we would buy her. Hubby wants something she can be buried with, something meaningful but the problem is she's materialistic,selfish and doesn't appreciate the sentiment. Sorry to talk negatively of her but that's the way she is.So all the usual ideas are out (photo albums, cards, messages, memory collections etc) and it's really upsetting my husband. We've brought her jewellery for the passed few years, putting a lot of thought into the gifts but they only get stashed away a few months later, never to be seen again (quite possibly pawned).
she's also depressed and still in denial that she won't survive this. We've organised a nice big family day for her but that won't be enough for her, she will want something to physically open.
This whole process is wearing my hubby down and tearing him apart from frustration, anger and guilt. I understand she had the right to be feeling the way she is and being a bit selfish but not at the cost of what she's putting her kids through and potentially my 4 young (8,6,3,2) kids. My youngest SIL is only 16 this year and my other SIL organised her wedding( that she didn't really want, they wanted to elope with close family) in 3 months to make sure her mother was around to be there.
I just don't know how I am going to get hubby through all this.