OP, seriously - grow a spine!
It isn't easy but it definitely works if you really want it to.
These type of people don't give a flying fuck about you - hence they're so thick skinned.
They use your good nature/sympathy etc to manipulate you - and you allow it
So what if she gets the hump because you refused to let her in?
So what if she goes around bad mouthing you - is that the kind of person you want in your life?
Last place i lived my neighbour from upstairs started stalking me like this.
She knew my 'routine'. When i changed it she would listen for the sound of my front door opening/closing and it was commented on if i didn't reply to her text/phone call
She expected me to 'hang out' with her every night, when i didn't she would make lots of noise in her living room, or switch the washing machine on at stupid 'o clock (my bedroom below) knowing full well i had to be up earlier than her
i had to be cruel to be kind.
i used the chain on the door when she knocked so she couldn't barge in
i shut the door on her whilst she was still wittering on - felt awful but but she refused to listen to 'i have to go'
I had to use some rude behaviours to put a stop to it
She bad mouthed me to everyone but i didn't give a shit - well worth it to be rid of her stalking
One time i had a neighbour from the opposite block knock on my door about 9pm ish
Well i wasn't in the mood for company,wasn't expecting anyone and just wanted to be left alone
She knocked quite a few times and i just ignored it
next day she walks up to me and says "i was knocking on your door last night and you didn't answer. i know you were in cos your lights were on"
To which my pissed off reply was "So? Just cos i'm in doesn't mean i have to answer the door!"
She was knocking to ask tell me that she wanted contributions towards plants etc for the communal garden & a rota for gardening duties.....it was council owned land & i was renting!