"Hasn't your mother told you she doesn't like your girlfriend? "Materne(nonne mater)non tua tibi dixit illam non amare amicam tuam?" I find this weird because I learned that a double negative in Latin makes an affirmative. Especially because it's a question with a negative meaning. I don't know if I'm being clear about my doubt. Can we construct sentences like this in Latin?
'Say that x is not the case' is routinely rendered by using a form of negare as the main verb with a positive infinitive in the indirect statement.
Also, if, as seems likely, the mother is the subject of both 'told' and 'like'), you need to use the reflexive pronoun se, not illam, as the accusative subject of the infinitive in the indirect statement.
nonne mater negavit se amicam tuam diligere?