I love scented candles and would be delighted to be given one as a mothers day gift, or at any other time. I think you're either into scented candles or not, if you're not then maybe you see them as a waste of money. Rebecons mum likes them though, so I sure she'll be really pleased.
My all time favourite is Jo Malones pomegranate noir, it's a lovely scent, not too cloying or overpowering but very recognisable. I'd much, much prefer a scented candle to a photo frame or voucher.