In modern times, discussion with regard to the definition and significance of virginity are largely subsumed beneath various pseudo-scientific doctrines and various forms of political theater, some of which you have already witnessed here. The biological foundation of virginity, however, has to do with the transfer of genetic information, both in the form of insemination (human DNA) and in the form of infection/infestation (viruses, bacteria, parasites). The distinction between sexual and casual transmission is based on the unusual properties of genital skin and orifices.
In the context of political theater, one may form any number of subjective opinions regarding sex and gender, and may therefore define virginity arbitrarily, generally with an eye toward establishing one's credentials as a member of a victim class.
In the context of human biology, a virgin is someone who has not had sufficient bodily contact to risk either pregnancy (in either party) or venereal infection; essentially, virgins are known quantities in the sexual market. Given that condoms and similar barriers are effective only against a limited range of venereal diseases, 'protected sex' constitutes a sufficient transfer. If you've penetrated someone with a strap-on, you have exposed yourself to sexual infection at least once and are therefore no longer a biological virgin.
There also exist theological and objective anthropological definitions of virginity, but I assume that they are not germane.
As Kitian pointed out, if you wish to debate the concept of virginity with this woman, you must first discover her premises. I suspect that one of those premises involves your anatomy; I suggest that you ask her what constitutes the loss of male virginity.
- N
