Sorry but I'm a grandmother as well as being a mother. If I were in your DM's position (I know I'm probably different), please don't give me smelly candles (or non-smelly). I have everything I want and everything I need so, if I were to choose a gift fr myself, it would be something to be used up. For example, perfume, wine, theatre ticket, coach outing, posh meal out with wine, reunion with a well-liked friend whom I've not seen for years or relation in similar position, photograph of an event I attended but never had one of the photographs.
Okay, I couldn't use up the photograph but I gave my parents a photograph of their wedding and they'd never seen it before. They were in tears and so pleased to have it. My grandparents had the original so I had a copy made.
I usually do a hamper for my DM, I tend to put in a calendar of family pics over the previous 12 months, some nice nibbles (local farm shop does amazing chutney, her favourite chocolates etc). Some smellies, a nice scented candle, and something like a pretty scarf or necklace. Things which aren't particularly expensive but she won't justify treating herself to as she spends most of her spare cash on me, DH and DS
My DM is very good to us; babysitting, lots of ironing, buys the DS' shoes etc. She's v much of the opinion that you can't take it with you and is incredibly generous. I'd like to do her a special stocking as well as her main present - but need help as to the contents. So far I've got the Elemis body milk (thank you xmas bargains thread) and an Orla Kiely notebook - more ideas please!