Take her somewhere she's been wanting to go, theater perhaps or nice restaurant. There does not have to be a 'gift' it's the experience that matters that's what she'll remember. Take some photos while your out, that way she has a reminder of the night.
For the two year anniversary gift, I would recommend a picture of the two of you in a nice engraved photo frame or a wood carved or hand made picture frame. Another would be to get an artist to draw both of you and frame it . If you already have given her a ring, a nice necklace, or watch would be great.
Well i would give her something based on how happy overall she has made me for the past two years and depending on what things she and i have been through together IE: if shes been more bad than good id get her something that says you need to get better than you are cuz you suck as bad as this gift i got you or if shes been a great lady these past couple years you get her something that screams how great she is and how you never wanna be without her!!! I could be more specific on an item but id have to know the status on the past 2 years... Ya pickin up what im putting down?