@maelstroon
She says she only finds valuable in herself when helping someone.
Thus, Rentarou tells her to NOT help him.
Because she's wiling to do anything to serve him, she does everything she can to NOT serve him.
Rentarou then reveals that it's impossible for her to NOT help him because she helps him purely by existing and loving him.
Therefore, since she's always helping him by existing, she is always valuable.