What color is she at right now? Continue giving her spa boiled eggs. Since its Boy and Girl version, just shower her with anything she likes. I did this, gave her 5+ gifts a day usually and got her to red by Fall Year 1. If you have a kitchen and a cheesemaker, try whipping up some Cheese Fondue. She absolutely loves it.
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There isn't really much else you can do but give her as many things as she likes in a given day and talk to her whenever you get a chance. Also, for the Tomato Festival, join her and her fathers team and do your best to win to increase her love points for you. If she invites you to her birthday in Summer, definitely go with a wrapped present (You can wrap at the supermarket) This will tremendously affect her love points. Watch the fireworks with her in Summer, ask her to a date on the Fall full moon festival, ask her to another date on the Winter Star Night Festival, Dance with her at the New Years Party at the Town Square, and ask her to accompany you for the Spring Goddess Festival.
If you can, make her Cookies on Spring 14 and give them to her.
Just be patient and so as much as I listed. You should be fine, Ann is relatively easy to get to red once you get used to it =]