Welp, a bit of a rocky ending but I enjoyed the story overall. Its a real shame the author had to cut the story short, I really felt like they were building up to something more with the MC. The chapter with her unknowingly running away from her own birthday party is still a massive gutpunch...
To be fair, I'm pretty sure the merchant has an item that she already used to genderswap them before so Lavi getting impregnated by his sister isn't impossible.