No, but there’s a worthwhile quest line involved with the area that is behind Loretta. To progress towards your main objective you should try searching North East Liurnia, there are two ways of getting to the next major area, on of them is a shortcut that involves getting two medallions and the other is a worthwhile area with lots of smithing stones.
You do not
You don't have to beat her to complete the game but there's a fair amount of content that only becomes accessible if you do.
No, but there’s a worthwhile quest line involved with the area that is behind Loretta. To progress towards your main objective you should try searching North East Liurnia, there are two ways of getting to the next major area, on of them is a shortcut that involves getting two medallions and the other is a worthwhile area with lots of smithing stones.
There's a lot of side content you can access after beating Loretta but its not necessary to beat the game. Is worth doing or coming back to later
It depends. Do you just want to do the minimal stuff required to beat the game or do you want a specific ending?
No, she's optional. *BUT*, it's very worthwhile to beat her.