]I love my G/F so much and she does to,but when I tell her that I love her she says to me that talking is easy and she want me to do something to prove to her that I truly love's her what should I do to make her understand that I'm crazy about her

Treat her with respect and continue being a good boyfriend, she will feel the love eventually.

The only way to prove your love is with consistent loyalty toward her and not abusing her trust in you. Spending money on her is not proof, words are not proof, jumping off a cliff is not proof. Like Javi said, as she matures and you continue to be loyal to her, she may finally realize you mean what you say. It sounds like she doesn't understand what love is.