說真的, 英文上很少人會用 "追" 這個字. 所以中文很普通的 "我在追她" 反而沒有最直接的翻譯.

I have a crush on her.
I have the hots for her
I am interested in her.
We are going out.

有 skirt chaser, Womanizer... 但意思就不是正面的...