I told this girl the other day that I thought she did her makeup and hair really well. Might have been a gay thing to do but..I did it anyway, since I really did like how she did both. She immediately looked down and she did she said "thank you". Why did she do this?
It could be as some people are saying that she was blushing from the remark. But honestly, the first thing I thought of and I think is the most likely scenario, is that it's an instinctual gesture of humility. That slight decline in the head shows that she is humble and is accepting of the compliment but doesn't let it inflate her head. I think a lot of people when accepting something humbly slight bow their heads when receiving it. It's an instinctual body language similiar to standing tall with shoulders pulled back shows confidence.
It's an involuntary expressing of emotion. No, she might not be blushing like everyone is saying, but it is an indicator of feeling shy or embarrassed. She could be a demure person or unaccustomed to compliments, and among other reasons.
HOWEVER, don't go over your head. It doesn't necessarily mean she likes you. :) I'm just letting you know because if you wonder about a little thing like this, she's obviously on your mind..
She deosnt no you ever so it could have been pretty creepy or awkward for her...yall are not friends so don't hope for a full blown conversation...that incident is to the equivalent of a girl saying "can you pass the salt?" and saying "thankyou" when you hand it to her then she look back down...she deosnt know you therefore she deosnt pay you or owe you any attention. hope I didn't come off harsh :)
She was hoping that a more attractive and appealing man would have complimented her(not saying you're a bad guy, that's just most likely what she was thinking). When she looked down, she was bracing herself and hoping that you would go away and not make things awkward.
Keep in mind, I'm very pessimistic when it comes to this sort of thing so take it for what it's worth.
I do not see anything unusual about her reaction or anything wrong in what you said or how you said it. If I see something worthy of a compliment on somebody, unless I'd be interrupting a conversation, I usually go right ahead and say it.