Targeting covenfolk of another covenant or even other magi with Creo Mentem magic instilling positive emotions is not against the Code per se. However, if it makes any other result easier, and accomplishing that result through magic would be against the Code, then it is an act against the Code. For example, if those covenfolk reveal secrets under the influence of magic which they would have otherwise kept hidden, under most circumstances counts as scrying. Magically convincing a magus to part with magical treasure counts as depriving him of magical power. Magically convincing a magus to vote the way you want counts as failing to respect his vote. And ultimately, there's that vague, catchall "endangering the Order" clause.
Making a maga fall in love with you so that you can have a torrid night of passion together? Fair game (unless, you know, it angers the faerie lord who's her lover). Making the covenfolk of another covenant like you, so that you get good food, a nice clean warm bed and the like? Fair game. Making a redcap feel that he really really should be extra careful about keeping that letter of yours safe? Fair game. Of course being legal, and being tolerated, are two very different things. There's always Wizard's War.