Translation:The farmers do not have trust in her.
Faith should be acceptable. In fact, if you check the De Bhaldraithe's English-Irish Dictionary for faith , you'll see that muinín is an option, and even appears in the example muinín, iontaoibh a bheith ag duine as duine
Do you mean another Irish word like English “faith” that can mean “trust”, like iontaiobh? Or do you mean another English word like “faith” that can mean “trust”, like “confidence”? One possible problem with using “have faith” is that it could be interpreted in a religious context, e.g. as if “her” were referring to Mary rather than to, say, a business partner.