Not so much under his thumb, they did go on the trip together, sounds like she trusted him at that point , she most likely wasn't thinking that he was going to spike her drink.
The more we're hearing, the more we're finding out that he appears to be in big financial trouble. She may have already known he didn't have money. He used his Marriott points for their place in Aruba, we don't know how he paid for the flight, he could have used frequent flier miles. He could have told her it was cheaper to get a bottle than pay for drinks at the bar.
Maybe she thought he was cheap but what was she to do, demand he buy drinks at the bar too, after he took her to Aruba?
JMHO