Is there a supplication for the guidance of someone we love?

Yes, there are many supplications (du'as) for the guidance of those we love and those we do not love, including: "O Allah, guide him; O Allah, make him a guide who is guided; O Allah, open his heart to the truth; O Allah, grant him success; O Allah, take him by his forelock towards righteousness and piety; O Allah, return him to You with a beautiful return." And there are supplications for guidance mentioned in the Sunnah, among them the supplication of the Prophet (peace be upon him) for the tribe of Daws: "O Allah, guide Daws and bring them forth," and his supplication for Abu Hurairah's mother: "O Allah, guide Abu Hurairah's mother," whereupon she embraced Islam, and his supplication for Jarir ibn Abdullah: "O Allah, make him steadfast and make him a guide who is guided." Supplication should be accompanied by certainty and chosen at times when prayers are likely to be answered, such as the last third of the night, between the adhan and the iqamah, during prostration (sujud), and after the Asr prayer on Friday, while ensuring one's earnings are lawful.