Luke had told her it was time to build a Lightsaber of her own, reluctantly she thought.

He had given her a copy of the instructions for building one that he found in Ben's home on Tatooine & not much advice beyond; "Take your time." Leia spends a day reading & rereading them, then weeks gathering the necessary components, reads the instructions twice more before she starts work.

The relief that she feels when she turns it on to find not only does it work, but does not blow up in her hands is immeasurable.