From the very beginning she is the only one who's been acting like an actual sister. She took the MC under her wing and has been trying to protect him. She's been talking and acting tough and bitchy, but that is actually how sisters do most of the time.
Not in my experience.
1 of mine is so much older she had left home by the time I was old enough to want or need an older sibling. The other was ever protective, the excuse for if my parents found cigarettes in my room the one to talk to when friends got in the shit and needed help. Then when she moved out and I was stuggling with my mid-teens her flat was the bolt hole to run to if I needed it.
Did we argue? Of course, but I argued with my parents and my friends too.
Did they wind me up and tease me? From time to time, but no matter what I thought then I see it now as them just having some fun.
Where they bitches to me? Only with good cause and that was usually because I had been a shit to them. But this was only for the duration of the row or whatever was happening, not everytime I say them.
It doesn't mean that she is your enemy or some major competitor about the important stuff.
Assuming Alice is your important stuff, then you are wrong, as it stands at the moment Leah is your direct competitor for her, more than that even, she is an obstacle to be overcome.
The guys complaining here about her don't seem to know what it means to have a sister. A real one.
It seems to me, as with all things in life, everyone's experience is different. My view of what it's like seems to be very different to yours yet mine is very real and unless I was to disrespect you I have to assume that you are not lying and your experience is real.
Broad sweeping statements are not generally helpful for constructive discourse. I try to avoid them, so would hope someone would pull me if I did it.