Przesiadała się w... or do?

First of all, please tell me if I am asking too many questions, and I will shut up :)

I found this sentence:

Przesiadała się w Londynie do San Francisco...

If I had written that sentence, I would have written it this way:

Przesiadała się z Londynu do San Francisco...

Which form, please, is correct?

no,

your version in english:

she changed from london to San Francisco

and original

she changed in london (on her way) to San Francisco

like esek said, this is the correct version. She changed in London (on her way/to go/to get) to San Francisco.