I'm going to tell my girlfriend that she says "I love you" too much
Do you think that she says it to you too much?
No, I'm going to tell her others say she says "I love you" too much.
It can be annoying when your partner does something that you don't like but you shouldn't try to control them. It is bad to control somebody, they will get tired of it and dump you.
I don't want to control her, I just want her to control it.
I understand that you don't want to be too controlling of your girlfriend, but that this kind of thing bothers you.  It might feel like it loses its meaning if she says it too often, but don't tell her that other people feel the same way if they haven't really said so.  It is important to be honest and open with those we care about.