Que tu l'aime means in English?

How you love her/him/it

que : how, indicate how much the love is

tu : you

l' : her/him/it

aimer : to love

"Que tu l'aimes" is not really a good structure of sentence, it's like we say "you love her so" without the "much" which means nothing.

In summary, french people usually says a more correct structure like "tu l'aimes beaucoup (=so much)"