This is wrong:
...since I've known her.
In fact, we use since with a specific time in the past, like: since 1999, since I met her, since I was 12.
In a sentence with 'since' your main verb should be 'present perfect'. This has nothing to do with what you use after 'since':
I have always wanted to travel to China since I watched that documentary.
I have lived in this city since 2011.
I have lived here since my childhood.
I have worked here since I moved to this city.