I have been one of the insouciant beholders to see the development of these 2 girls' friendship. The reason Why use friendship instead of any vacabulary higher than that is probably the heterosexually oriented girl is feeling so disturbed by the deeds of her bisexually oriented partner.
It is not judging anything regarding the sexsual attractions or orientations, it is about showing respect to personal choice to avoid embarrassment and fortify a normal colleague-relationship and friendship in workplace.
There is a profound and universial aversion to being forced and restrained, especially the reality is revealed since the beginning that the girl loves her boyfriend and her boyfriend loves her, they have been separated geographically for years, but they don't change anything. If retaliation really needed, at least do it properly, not that sentionally. Don't forget that it in office.
It is not only the matter of 'I kissed a girl', but also the matter of listening, everyone deserves respect.
update:
they found a solution after all of us knew their story...actually the explanation given by the bisexual is I am kidding for what I said, you overreact, I treat you as my best friend. The suggestion from the heterosexual is I don't like the feeling of your overwhelming treatment, keep friendship at normal level.
Over kidding, over reacting, we all are blind.
That's it.