I dispair !
I congratulate Apple on their strong security posture, they are known for it, and un-jailbroken iPhones/iPads are pretty much the most secure thing you can get your hands on if configured correctly.
There is no need to know the password. You can just do a simple system erase and re-install the operating system via iTunes. It takes less than 10 minutes. Obviously you won't get the previous user's files, but you will have a perfectly usable device for your own uses.
And anyway.... she could have just left the password in her will !