Keeping some files & passwords on old mac while deleting others...how to?

I got a new mac and want my assistant to be able to use my old mac for certain files and passwords to websites that are already saved. How do I remove my personal passwords and files without erasing them from my new Mac? There are some business websites on Safari that are bookmarked and have the passwords saved that would be convenient for her to be able to access but I don't want her to be able to access personal bookmarks. How do I separate the two computers without erasing all of the data but being able to keep some?