He paid for her flight. She thinks she's our girlfriend. We're lost

There's a single woman we've been seeing for about seven months. Started as a unicorn we met through Wyylde — flew out to meet us in Miami for a long weekend, clicked, became a recurring thing. She lives in Chicago, we're in Austin. Around month four we started paying for her flights. Around month five she started staying a full week instead of a weekend. Around month six she stopped seeing other people. She's told us she loves us, in those exact words, after a glass and a half of wine and not retracted it in the sober morning. My wife said it back. I did not, and now my wife is mad at me, and our girlfriend (?) is going home tomorrow. Here's where I'm stuck. We agreed before all this that we weren't poly. We were ENM, scenes, recurring play partners maybe, but not a third person in our marriage. Somewhere along the way the flights and the toothbrush and the dog she befriended turned into something that is not what we signed up for. The money part — I keep thinking about the money part. Is this a girlfriend or am I subsidizing a girlfriend my wife wants me to also love?