Someone sold me an iPhone on Ebay and She forgot her apple ID and password.

The only thing you can do now is to try and get your money back or recycle the phone responsibly. Without the Apple ID credentials there is no way to use the iPhone.

Activation Lock for iPhone, iPad, and iPod touch - Apple Support

Hello ~ If she cannot or will not remove the activation lock you will never be able to use the iPhone. Take a look here:

Activation Lock for iPhone, iPad, and iPod touch - Apple Support

Also:

The All Too Common SAD Reality of Buying a Used iPad/iPhone

Try this file a claim through eBay that the item was not as described and go from there. Did the seller say it was unlocked? Either way …you have nothing to lose. Give it a try.

~Katana-San~

Activation Lock is designed to prevent anyone else from using an Apple device if it's ever lost or stolen.

Activation Lock for iPhone, iPad, and iPod touch - Apple Support

Activation Lock is an anti-theft feature that cannot be bypassed. Only the previous owner can remove the lock by using their Apple ID & password. Apple will not help you find the previous owner. If the previous owner cannot or will not remove the lock, then the device is useless to you or anyone else. Try to get a refund (through eBay) or dispose of the iPhone properly. See the 'Check for Activation Lock before you buy a device from someone else' section in:

Activation Lock for iPhone, iPad, and iPod touch - Apple Support

or

The All Too Common SAD Reality of Buying … - Apple Community

If the woman who sold it explicitly stated it was Activation Locked on eBay then you have lost your money and recycle it responsibly. If she did not then tell her you want to return it for a refund. If she refuses turn to eBay's fraud protection.