It all depends on the context in which you use this term.
1) Trap Queen might refer to a song by Fetty Wap
She my trap queen
And in that case Trap is a place where drugs are sold.
2) A girl with large trapezius muscles.
Look at that girl hitting the gym, she's a real trap queen
3) the person is a queen for traps, with traps meaning boys dressing up as girls, mostly in anime.
She is so cute, but she is a trap queen, so she is really a he.
4) @katatahito's answers is also correct, a girl that is very loyal can be called a trap queen.
My girl will always be with me. She is my trap queen!