So just to let you know I am 20 and was hanging out at my friend's house earlier today. We were outside talking when his girlfriend pulled up with her cousin and friend. They are all Bosnian, and I'm American. His gf came up and started talking to him, and I went inside to get a soda. I was a little embarassed b/c I was wearing a wifebeater. As I came back out, his gf said, "My friend thinks you're hot."
I didn't really know what to say, so I just said in a C+F way, "she's right." Then I leaned against my truck and started drinking my Mountain Dew and her cousin (HB

came up and said something in Bosnian. I responded with "...what?" My friend started laughing and HB 8 asked if I was American and I said yes.
She then led me to the car where the supposed friend that likes me was. She was pretty ugly, so I just said hello as the cousin got into the car. HB 8 said "You're really cute" to which I said "thank you." I was so tired and didn't feel good, so my confidence was a little down, but it felt good to get a compliment.
I was wondering if she was looking for a compliment in return, but I didn't want to give one. (Should I have?) My friend's gf mentioned that HB 8 had a bf. Then HB 8 said I had pretty teeth, and I said thanks I had braces. (I know this is dumb, but I really wasn't trying to hit on her especially b/c she had a bf and they were giggling)
Then she said "Don't tell my bf, but would you flex your muscles?" (I work out) I said point-blank "No" She asked me again and I told her that my friend was stronger than me so he can flex. Then my friend's gf got into the car and they drove away.
I obviously wasn't concerned with picking her up, I just didn't feel like it, but I sometimes get compliments like these and I'm just wondering how I should respond in a 'real' situation? Thanks.