These days you have to be careful what you say to anyone. Just compliment her on her hair and style of clothing. Notice when she changes her hair or type of clothing. Tell her what you admire about her, like the color of her hair, or her eyes, or the perfume she wears or the way she laughs, etc. Be observant to her and make her know that you notice her being.
Also, don't only complement her looks. Of course, you need to complement her looks, but complement other things too. Laugh when she jokes, tell her she is interesting to talk to, or complement her for how passionate she is. If she plays a sport, tell her she did great. If she is nervous about a job interview, tell her how smart she is.
Answer....-Blank stare- What are sweet things to say to a girl you ask? You say things that come from your heart. You don't ask what to say to her, you should know what to say to her. Tell her how you feel about her. Tell her your thoughts. Common sense. I don't mean to sound rude but come on!... whatever comes to your mind that you know she'd like to hear tell her...I'm sure she'd love to hear what you think of her.
************ One more thing to add, any girl will love it when you give her a nickname some favourites are love, sweetheart, belle (means beautiful in french). If you call your girl any of these things regularly her heart will flip whenever you say it to her*************