"You should not lose to her."
Translation:S ní bys neměla prohrát.
My first instinct was "you should not lose with her" (on your team), given we've just been learning "s" as "with". Is there something about the form of the rest of the sentence which makes it "lose to her" rather than "lose with her"? And/or how would you say the latter in Czech - "You should not lose with her"? I'm not questioning the translation - it's just curiosity mainly. Hope all are safe and well.
No, that would mean "You shouldn't lose her" (in a game), it could also mean " you shouldn't lose it" provided that the "it" is a feminine object - for example a bet ("Neměl bys prohrát sázku.")
The sentence "you shouldn't lose to her" means you will probably win a game that you play with "her" or a bet. It has to be "s ní". Another way of saying it would be "proti ní" (against her), but that's not among the accepted translations as it would unnecessarily inflate all the possible correct answers.