It's the time to raise this issue if you want to renew the contract with her. If you do not give any hence, they may think you are not planning to renew the contract and will start to look for a new employer two to three months before expiration of the contract. Or they may not want to renew the contract (in this case, they usually will not answer you at once). Then, you will have enough time to find a new one.
If both of you reach an agreement to renew the contract, it can be proceeded a month before the expiration date.