Minimo Cynically, I would be very dubious about this sudden show of affection, thinking that your MIL had suddenly realised that she would need your support and care from now on.
My MIL hated me before we had even met and found fault with everything I did or didn't do. Nonetheless, having accepted that we would never be close, I did my duty and was unfailing kind and concerned to her face. I must admit I took a perverse pleasure in annoying her by lavishing praise upon her in public, taking her small gifts (straight in the bin) while sharing my real thoughts behind her back.
When she broke her hip and we rushed to hospital, she kept asking 'where is my son' (He was away filling in the admission forms) and the nurse said 'never mind your son you have your daughter here'. She went ballistic, dropped my hand saying that I was no relative of hers. The nurse made it worse by remarking that she had made the assumption because I looked so like her. Ironically, she collapsed at her DH's funeral and later died in MY arms.
My lasting feeling is great sorrow for her. A clever woman who was miserable for most of her life and lost all her friends/relatives even the love of her DGDs by her actions and cutting comments. I have no guilt about how I treated her. I did my 'duty' by her while trying to protect my DH, DDs and her DH from the worst of her excesses. I never had a word of thanks from her but did have recognition from the rest of the wider family for having 'the patience of a saint'.