@Kevadu two-timing refers to when someone cheat or otherwise have a relationship without the consent of their partner. In the words of almighty google: two-time /ˈtuːtʌɪm/ - deceive or be unfaithful to (a lover or spouse).
Asking for consent and still calling it two-timing is weird in the first place, but not unheard of. It could still be called (but normally wouldnt) two-timing if you have a mistress/a habit to visit a bath house (thanks kingdom come for teaching me this euphemism), even if your partner is aware of (and agreed to) it, simply because the other girl is not considered a proper partner. You would mostly see this unusual case in rich or noble families, who married for more political reasons. Sometimes with contracts to ensure that it is kept on-the-low, hush hush (So they don't get shamed in society as a man/woman who can't please their partner).
As an opposing thing to two-timing, there are polyamorous/open relationships, and iirc there was even a phrase specifically for ones where several ppl were mutually in love (which with her reaction to the girl could end up the case here), causing a literal love triangle (hurr durr).
Asking for consent and still calling it two-timing is weird in the first place, but not unheard of. It could still be called (but normally wouldnt) two-timing if you have a mistress/a habit to visit a bath house (thanks kingdom come for teaching me this euphemism), even if your partner is aware of (and agreed to) it, simply because the other girl is not considered a proper partner. You would mostly see this unusual case in rich or noble families, who married for more political reasons. Sometimes with contracts to ensure that it is kept on-the-low, hush hush (So they don't get shamed in society as a man/woman who can't please their partner).
As an opposing thing to two-timing, there are polyamorous/open relationships, and iirc there was even a phrase specifically for ones where several ppl were mutually in love (which with her reaction to the girl could end up the case here), causing a literal love triangle (hurr durr).