There is no culture test for molluscum.
In any case, while it is true her HSV-2
ELISA result is on the low side, it is
in the positive range and entirely consisteng with her being infected with HSV-2.
Your story is quite typical. Genital herpes due to HSV-2 often appears in truly monogamous couples, either because the infected person has had it all along, but previously had no symptoms; or because his or her partner had it all along, and transmission only occurred recently.