When Fern said it's been half her life she's know Frieren pretty sure what she meant is that she was like about 8 years old when they first met at Heiter's place and now she's 16.
Himmel is such a Hero that even the illusion of him couldn't help but heroically encourage Frieren to take the correct course of action. 'Frieren, shoot me'. Also amused that you seemed so caught up in what was going to happen to Fern you didn't notice Frieren talking about her master begging for her life.
I really feel we are being 3-D chess manipulated into watching an anime prequel that hasn't even been made yet. If they made one I don't think I would have any choice but to watch it
One think I really love is how every time something tries to use Himmel against Frieren it backfires because he's such a nice, selfless, person that he tells her to destroy him rather than risk harm coming to her. . On a related note: my gut feel is that she will go and have the conversation with Himmel, who will tell her something to the effect to go and have a good life and that he will be waiting for her when she eventually joins him.
Fern was doing basic math, she has been with Frieren since around the age of 8. Thus she has literally spent half her life with Frieren at this point, wouldn't take many years for that to be the case at such a young age. In addition if one assumes that the journey her and Frieren are now embarking on is at a minimum the same length as the Heroes party was then that will total 18 years and she will be 26 so at that point it'll be more than half her life.
