apparently bella can be found in the comunity lots in strange town but I think it is a random thing, so she isn't always there. personally I've never seen her but I've only ever entered the comunity lots a couple of times.
as far as I know you can befriend her through another sim. ( named in first post)
the information posted is what I have gathered from my own gaming and other threads relating to these questions.
wish I could help more, if I see bella myself I'll let you know
