Q: I am the new owner of iphone 5 and the past owner forgot her i cloud how can i do this help me      

No-one can help, you must get her to unlock the iPhone or you can not use it. I would ask for your money back at this point.

You are out of luck. Your only hope is for the previous owner to recover her icloud credentials through the proper channels with Apple.

You need to contact the seller and ask him to remove this iPhone from his list of devices. Otherwise, your iPhone will be a useless brick.

Find My iPhone Activation Lock: Removing a device from a previous owner’s account - Apple Support

The only other recourse is if the ORIGINAL owner has the receipt for the phone.  Take the proof to an Apple store and they may be able to reset the phone.  Otherwise, as others have said, it is useless to anyone.

So far as I know, there is no Apple Store there. You can find links to authorized resellers and service centers here: https://locate.apple.com/ph/en/