The original owner of an ipad accidentally activated her ipad to use "Find my iphone to link it to their Apple ID". The problem is that she doesn't have an iphone and she doesn't remember her apple ID or password. What should she do?

This page should tell you everything you need to know relating to both the Activation Lock - and how to recover access to your AppleID and password:

https://support.apple.com/en-us/HT201365

You will be directed to this website:

https://iforgot.apple.com

If you are unable to find out what apple ID has been used to lock it you will not be able to unlock it by yourself

You may still be able to get help from apple to unlock it if you can prove you are the owner of the iPad, Find the purchase receipt

And:

Contact Apple for support and service - Apple Support

Good luck!