Your wife has a good women's intuition tuner, you should trust it.
If you would like to meet up with this old flame my suggestion is:
Tell her that you would love to go to dinner with her husband/partner and that your wife is making reservations for FOUR. If she comes back with, well there is no husband/partner and she was thinking about how much easier just meeting you alone for coffee would be, she is looking for a MAN.
If she really wanted to catch up with you, she would have invited you AND your WIFE to dinner or to some other similar thing, Because catching up with you, means including your wife who is part of who you are.
A little story, my friends husband had a HS reunion coming up, an old flame got his email from the reunion planning committee. Pretty soon she was emailing and calling etc. He was kind of flattered, but thought she just wanted to remember HS days and no big deal. At the reunion, this "lady" would come and stand in between him and his wife and keep her back to the wife while telling him how good he looked, laughed at his stories etc. After the reunion, and my friend was steaming, he figured he would never hear from her again. Oh no, now she was going to travel to his state and wanted to meet for dinner, just him. My friend had had enough at this point, said no more phone calls, she can email BOTH of us instead. Next the old flame starts calling him at work...He finally had to put a stop to it telling her, that his wife of ALMOST 50 Years was the woman in his life and he was not looking for her to replace his wife.
Trust you wife's intuition!