I want to marry Celia. It's taken SO many years on the game (5-8 years..

u buy a love pendant from harvest sprite company casino and use it when giving thing to celia.that way u can make her heart go red in 1 year

Make sure you aren't littering. That decreases affection and friendship of all the townspeople. That's the only thing i can think of that could be making it so slow. You should also visit the sprite tree and get the Love Bangle, which, when equipped, will show you how much affection and friendship you have with a person. You can use this to help you figure out why it's going so slow.
Just for reference, Celia's favorite present is cake, and her next favorites are Yarn, Perfume, Diamond, Pink Diamond, Curry Bread, Risotto, Dry Curry, Curry Noodles, Curry Rice, Blue Curry, Green Curry, Red Curry, Yellow Curry, Orange Curry, Purple Curry, Indigo Curry, Black Curry, White Curry, Rainbow Curry, Ultimate Curry, Finest Curry, Doria, Grautin, and Elli Leaves. Cake increases love points by 800 and the rest increase it by 500.
Note: you can only increase a girl's love points ONCE every day, so each subsequent present will increase friendship.
Heart colors:
10,000 to 19,999 - Purple Heart
20,000 to 29,999 - Blue Heart
30,000 to 39,999 - Green Heart
40,000 to 49,999 - Yellow Heart
50,000 to 59,999 - Orange Heart
60,000 to 65,535 - Red Heart