Does a person's love for his grandmother and his desire to accompany her in Paradise conflict with his love for the Messenger, may God's prayers and peace be upon him, and his belief that the Messenger is more precious?

There is no harm in loving one's parents and relatives, but faith is not complete until one loves the Messenger of Allah, peace and blessings be upon him, more than all of them. Lofty aspirations are required, so a Muslim's heart should be attached to the companionship of the Prophet in Paradise, by loving him and obeying Allah and His Messenger. Whoever obeys Allah and His Messenger will be with "those whom Allah has bestowed favor upon — of the prophets, the steadfast affirmers of truth, the martyrs, and the righteous." This does not negate your reunion with your grandmother in Paradise, for the child who follows their parent in righteous deeds will be joined with them by Allah, as stated in His saying, "And those who believed and whose descendants followed them in faith — We will join their descendants with them."