Flowers and take her out for a meal with the family? Lots of older women don't really want more 'stuff' I think. Certainly all of the presents we have ever bought dp's mum have been a waste of money! The only thing that went down well was a photo frame with a picture of dp and the children (I was in it too but I think she would have been just as happy for me not to be!).
Agree with janeite - my mum is 61 and she doesn't want stuff. Unless she has something broken that wants replacing - perhaps you could ask your mum if she needs anything like that. I would agree with a meal out with family (have you got any siblings you could invite?).
Does she have any hobbies? Gardening, walking, cooking etc etc? So a lovely preplanted pot of something to flower is nice if she likes that kind of thing or a book on her subject of choice, a selection of exotic and interesting herbs and spices etc?
Digital photo frame with preloaded pictures of you, the DGCs etc?
Something beautiful for no reason besides that it is beautiful - eg a handblown glass bowl or vase, a beautiful wooden box or chest for knicknacks etc.
Something luxurious - cashmere cardigan, silk dressing gown etc.
A weekend away with you if she doesn't have a partner.