Both "you too" and "me too" can be used to express that you love the person who said "I love you."
"You too": If someone says, "I love you," and you respond with "you too," it means that you are saying, "I love you too." In this case, you are affirming your love for the other person.
"Me too": If someone says, "I love you," and you respond with "me too," it means that you are saying, "I love you too." In this case, you are affirming your own feelings of love for the other person.
Both responses are commonly used and understood to express reciprocity in love. The choice between "you too" and "me too" depends on personal preference and the context of the conversation. Both forms are considered correct in this context.