My girlfriend from USA is traveling to the UK through Manchester next month. She has a visit visa in her passport for travel since she was refused entry last year. Will she have to scan the MRZ on her visa page, or the bio page? Also, will the gate even work for her given her previous immigration issues?
Will she have to scan the MRZ on her visa page, or the bio page?
Your girlfriend will need to scan the MRZ bio page as that is the way the computer will read the information, using the chip on that page.
Also, will the gate even work for her given her previous immigration issues?
There is a possibility she will be sent to the passport control officers, there is no harm trying to use the gates.
One should only scan the front of the plastic card/page, like the immigration agents do.
The front of the card has 2 or 3 lines of OCR text, this text is used as a password to read the info of the RDIF chip in the plastic card.
Having this security ensures that no one can read that info by e.g. tapping a phone against your pocket/backpack.
There's an excellent Android app called ReadID that can read your passport the same way the eGates do. It will even verify the digital signature of your passport against known digital passport issuers (countries certificate authorities). The signature is just like those used for HTTPS.
Also, the visa is digital, you don't actually need the stamp, though most countries still require it.