This reminds me of critics who claim they can't believe in evolution because they can't see it happening.
To be fair, too, you can probably also claim, in her line of work, that monogamy doesn't work either. What are the odds she has seen or know of a lifelong marriage?
Only about 50% have hit 40 years.
(Tables 4, 4a, 4b)
Even worse, the rate of marriages hitting 10 years fell from over 80% to under 80% in the last 50 years, attributed to ease of divorce and changing social norms. The good news is that the rates are going up again, since 1975.
So the point is, really, selection bias. Her livelihood is dominated by failures, not successes, and the more people involved in any endeavor, the more points of failure there is. That's how hardware works; moving parts are failing parts, and the more moving parts, the more failing parts.