For дівчина to mean "girlfriend" it rather needs to be "owned": моя дівчина (my girlfriend), дівчина мого брата (my brother's girlfriend). Just дівчина is usually "girl"

No. Laughing and smiling are two different things in English and all the languages I know. I have checked Ukrainian on Google Translate and it uses the word "сміятися" for "smile". Out of curiosity, does your native language use the same word for "smile" and "laugh" ?