The NHS pension has no simple answers. Assuming she wants to claim without reductions for early payment:
The pension she's earnt since April 2022 can be claimed at 67.
The pension earnt between April 2015 and March 2022 can be taken at 67 or whatever the age is for the rest of the pension below. At 67 it will be worth more, but she won't get it for as long as if she takes the lower value earlier.
The rest of the pension might be 55, 60 or 65. This depends on whether she paid in as a student, whether she was part of the misselling that led a lot of students to withdraw their pension payments at qualification, the exact date she started work, whether she's had any breaks from nursing (or from paying into the pension while working), what choice she made in Choice 1 in 2008 or Choice 2 in 2015, and whether she's employed in a nursing role at the point of retirement.