There's loads of reasons why she didn't kill her etc
1. Lisa thought she killed her by whacking her over the head, so left her in the cabin to either rip her face off or something evil like that.
2. Lisa got scared when Jill came into her Cabin, which nobody has done in years, so she hits her and makes a run/swagger from it.
3. Maybe after all the deaths she's caused to people that reminded her of her mum, maybe Jill stood out to her as a Mum and didn't want to kill the one thing that made her happy/fell good inside, so knocked her out, so she could keep her in the cabin.
There's many more reasons, but these three stand out for me. Lisa Trevor is a very interesting monster in the game, it made the remake a joy to play for the first time and many people forget her and only remember Nemesis and Birkin as the best monsters, but she has some great backstories and really sums up how evil Umbrella actually are.