Luna was trying her best to incorporate the pure mana she was accumulating directly into the spinel.
She planned to put the spinel to the weapons and allow her group and a few others to fight against the nightwalker without needing the attack they were doing now.
She chose a spot that is isolated but not too far in case something were to happen with the others, she would be able to give her support as soon as she can.
What she did not expect was that it was not them who would need her support but it was her who would need their support.
She had chosen a relatively isolated place and did not feel anyone tailing her. She simply did not think that someone would trail her using their ability. This is something she could not detect, the same as when Aaron placed a strand of wind on Genevieve during the first month of their meeting.
Even with her strength, if one person has trained his whole life to be a tracker, it would be difficult to detect it.