This is new to me cause im 22 and this is the first year I have been in a serious relationship and want to take a girl out. The the thing is she is cutting sweets out of her diet and my plan is to take her on a nice dinner and try to convince her to have a cheat day where she can eat whatever she wants. Then we can share a bottle of wine. I also picked out her favorite sappy movies that I hate but she loves. I just don't have a gift idea for her because she the traditional bottle of wine and sweets isn't what she wants and its kinda a staple of the holiday.
Look into Paleo cherry brownies they are sweet but are good healthier options. Wine is tricky but I am sure if you do some hunting you can find some organic wine go for a bolder red and avoid moscato and reislings. Or get her some turkey jerky, and a bottle of green smoothie mix... but make it funny... good luck! Crap now I gotta think of something for my guy... Hooters and Deadpool movie done!
Try the edible arrangements (it's fruit)! They're pretty and fresh and delicious. :) You may be able to talk her into a bottle of red wine, it's actually pretty decent for your health. Antioxidants and stuff.
And you can always take her to a nice dinner if you want. Most every restaurant has healthy options.
Take her outside to a pinic with mini sandwiches. Or a nice veg and chicken salad and take a walk near a forest or a park and eat there. The best gift you could give her is your effort and time and love and respect. Spend time together.