"Buy her medicine" can mean "Purchase medicine for her" or "Purchase the medicine that she [makes and/or] sells". Both are imperative sentences, in which the speaker or writer instructs or commands the person spoken to purchase medicine. Just which meaning is the "correct" one take depends on the context and any preceding sentences, but I would normally say the first meaning I gave above is more likely than the second.
"Find you the right partner" could be a sentence, such as would normally be written "You find the right partner", but as it stands it appears to be a sentence fragment, the middle part of "I will try to find you the right partner to dance with."