I got her a card, and even at that I didn't want to.
For two reasons. The first being that I don't get on with her. The second being is that I don't see why one (largely commercial) day is any different to another. It's not like we're celebrating a birthday or Christmas, but these silly one day fads such as Valentines Day (seriously, wtf?), Mothers and Fathers day... it's just a load of bollox. I don't treat it any differently to any other day. If either my Mum, Dad or my GF were to expect any sort of special treatment on said days, then sadly they'll be disappointed.