I made a bet with with a girl. If she won the bet I would give her a higher tip. If I won I would have her as a date. Was this deal unethical?

To expand on the story, she is an attractive hairdresser that I have been patronizing for years. She is long divorced but very attractive and we converse quite a bit. She ended up losing the bet over how long it would take my hair to grow. I felt like I kind of baited or tricked her in to the deal, but I do have her consent.
I made a bet with with a girl. If she won the bet I would give her a higher tip. If I won I would have her as a date. Was this deal unethical?
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