Ah... That's a great psychological incite and would have made a story more profound should this development be more pronounced.

Jan has someone, but she sort of overgrew him professionally (as she makes more money) and personally - she keeps herself in shape, has a great personality, etc. Inside she's much younger than her age. So she looks at younger men as more appropriate partners.

So she doesn't invite her partner to the corporative get-together and does a class act dancing with Toby. She just wanted to be a center of attention, to "shine" so to speak, to feel a younger man's interest and feel the envy of women, but then something stops her. Maybe it's thought of her marriage vows that she doesn't want to break? Or maybe a realization that with such a large age gap there cannot be anything lasting?

So I'd say this story deserves a rewrite and then be added to your portfolio. 😉