There are three ways I would go about this.
1.If she is a stranger she could be flirting with you or being friendly. Without any body language or context it's hard to tell.
2.If she is a college, friend, or a person that works there ALWAYS assume that she is using it as a term of endearment and that she is comfortable with you but don't assume she likes you romantically because it usually doesn't go well. Many women do that to be nice. You can ask her but be prepared to play it off like it's nothing or it will be awkward.
3.If she is older than you than it is common for women to use "darling", "honey", "baby", etc(especially in southern US) when speaking to someone younger than them.
But, these are experiences from what I have seen, read, and heard, also experienced myself.
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Autism is a disorder not a personality trait!
"God grant me the serenity to accept the things I cannot change,
Courage to change the things I can,
and Wisdom to know the difference."