Ask around and see what she likes to drink, if anything. If she likes prosecco or red wine then a bottle is good. I hate silly gifts they are such a waste of money. I may be unusual but I don't like yankee candles. My favourite would be a voucher, I know people always say it isn't personal but I like choosing something.
I don't like Yankee candles either. I'd be disappointed with a mug too (although have both given and received them in the past) - we have so many mugs, and I always drink out of just two of them.
I'd always be pleased with: nice notebook and pen funky Post-It notes Prosecco Nice chocolate (tiny box of something good, rather than big box of Celebrations-esque stuff) Biscuits - M&S tin of shortbread or something like that book marks (can never have too many!) Coffee / nice tea bags