I'm one of those girls that often hears, "I was so intimated by you when we first met!", "I always thought you hated me!"
I've quizzed my friends on why people get this impression and gotten a variety of answers, " You're cold if you don't know someone well.", "You don't wear your heart on your sleeve.", "you've got the resting bitch face.", etc.
It's not always a bad thing to not be 100% approachable but I wish people could see that most of that is I'm typically really shy and reserved when I'm around new people. I wouldn't want to dispel it completely, there's mystery in a stoic woman but I wish people could see that under the surface I'm just a really goofy, warm hearted, ditzy girl.