imo, this is a good character development for her. She got traumatized and felt not enough after seeing Rudeus die in front of her. So, she's going to train to improve but then again. It would be really really nice if she wrote a letter that was not vague. this dumbdumbixch hahahaha like. Sis, your words will be very confusing for Rudeus to understand (especially, leaving him after doing the deed). I hope before leaving him, she could have told him her plans.
Anyways, it is always good to be a better asset for him. Other readers may think she doesn't need to be strong after all she is a "woman" but seriously you cannot undermine her with gender after being so involved with many adversities with Rudeus. She knows she needs to be strong to support the mc regardless of him being capable of "protecting" himself. She just needs to satisfy her incompetencies, then return. Hopefully, she TALKS and EXPLAINS to him PROPERLY why she distanced herself. srsly conflicts happen because people don't communicate.
srsly ghosting after sex hahahaha a dck move if she did have one.