Acts 16:16-22

And it came to pass, as we went to prayer, a certain damsel possessed with a spirit of divination met us, which brought her masters much gain by soothsaying: The same followed Paul and us, and cried, saying, These men are the servants of the most high God, which shew unto us the way of salvation. And this did she many days. But Paul, being grieved, turned and said to the spirit, I command thee in the name of Jesus Christ to come out of her. And he came out the same hour. And when her masters saw that the hope of their gains was gone, they caught Paul and Silas, and drew them into the marketplace unto the rulers, And brought them to the magistrates, saying, These men, being Jews, do exceedingly trouble our city, And teach customs, which are not lawful for us to receive, neither to observe, being Romans. And the multitude rose up together against them[.]

Strong's numbers:

Damsel - παιδίσκη
paidiskē
pahee-dis'-kay
Feminine diminutive of G3816; a girl, that is, (specifically) a female slave or servant: - bondmaid (-woman), damsel, maid (-en).

Spirit - πνεῦμα
pneuma
pnyoo'-mah
From G4154; a current of air, that is, breath (blast) or a breeze; by analogy or figuratively a spirit, that is, (human) the rational soul, (by implication) vital principle, mental disposition, etc., or (superhuman) an angel, daemon, or (divine) God, Christ’s spirit, the Holy spirit: - ghost, life, spirit (-ual, -ually), mind. Compare G5590.

Divination - Πύθων
Puthōn
poo'-thone
From Πυθώ Puthō (the name of the region where Delphi, the seat of the famous oracle, was located); a Python, that is, (by analogy with the supposed diviner there) inspiration (soothsaying): - divination. [Only occurs once in the Bible.]

Gain - ἐργασία
ergasia
er-gas-ee'-ah
From G2040; occupation; by implication profit, pains: - craft, diligence, gain, work.

Soothsaying - μαντεύομαι
manteuomai
mant-yoo'-om-ahee
From a derivative of G3105 (meaning a prophet, as supposed to rave through inspiration); to divine, that is, utter spells (under pretence of foretelling): - by soothsaying. [Only occurs once in the Bible.]

 Now, my questions are these:
Why did it bother Paul? I mean, she was bearing testimony of them. She was, in essence, saying, "Listen to these men. They're servants of God. They show us the way to salvation."

Did he just get irritated because she was rather like a groupie?

Was it because she was female (Paul's other writings show him to be rather misogynistic)?

Why do we assume/teach each other it was a devil? Maybe it was a gift inside of her and not an actual separate being possessing her.

Wouldn't her testimony cause others to listen to Paul and his companion? Didn't the Lord say that those who are not against us are for us?

Is every spirit that possesses people from God? Is every gift of divination from God? Do some "gifted" people simply make things up? If they testify of the truth, are they of the wrong spirit? If they testify of truth at times and make things up at other times, which spirit are they of?

And, seriously, did this girl just irritate Paul because she hung around him - or were her masters making money off of Paul's presence? You know, hanging around him and putting in her own little prophecies and teachings on the side, which brought money and attention to her masters.

In other words, maybe they were sharing their own teachings alongside Paul, but that was not written in the record we now have.

I dunno. It just seems strange that he would get ticked off at her for testifying that they were true messengers of God.