Maybe she doesn't want the committment and likes the idea of an easy out.
Astrology could explain this to a "T" but a sinlge woman engaged in a 5+ year affair could be actually be the twin flame or soul mate to this man...life is a pecuilar matter and we must not treat it or understand it like its "normal"
She loves him.
They could be soulmates
He must have a big "thang."