So let me see… an employee brings along her new boyfriend to a work function; has that boyfriend stolen at that very same function by another woman in the office; then she has to put up with that woman coming in and gloating and showing off rings and so forth; it sounds like a living hell.
To make matters worse, you:
a) make her sit next to the woman who did this;
b) think she should “find someone else” because that’s what “they do”.
c) blame the aggrieved woman for all the workplace problems (if only she would leave these personal feelings about it at home).
You don’t want to hear my judgement about your attitude to women or ethics as a boss, but I’ll just say it isn’t good.