Someone I love has an very bad planetary placement in their birth chart. But I know he will not recite hindu mantras. If I recite the mantra instead her, will it have any effect?
You can send her good energy, but you are already sending her bad energy by making weird judgements about her birth chart. This is effectively like a curse, what you fear you manifest. Your thoughts have power. So you would do well to just stop judging and leave her alone.
Lakshmi mantras may be what you’re looking for