As far as the form of the contract is concerned, it has no effect. A contract is an expression of the true meaning of both parties. There is no your signature or handwriting on this contract. Can be regarded as not what you really mean. Your girlfriend signed the contract on your behalf, and the other party thinks that your girlfriend has the right to sign the contract on your behalf and with you. But the final signature should be your signature or your girlfriend's signature. But here your girlfriend signed a fake name, which means that both you and your agent have expressed their true meaning. The contract will not take effect.
I suggest you look at the time of signing the contract. If the time is not long, notify the other party to cancel or re-sign. Avoid future disputes.
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