I ain’t sure if i understood what you wanted to know, but you can actually attach a bunch of differents verbs after “qui est” as long as it makes sense.

For exemple, you can say “Une amie qui est passée près de chez moi m’a dit bonjour”.

It is not a direct contraction, you can’t just remove “qui est” in every case. Moreover the first sentence would work better with some commas.

In the second sentence you have a “proposition subordonnée relative”: “qui est venue faire du tourisme à Kyôto”. This kind of construction works like an “adjectif qualificatif” to give an information about a noun (here this noun is “amie”).

There is an other kind of construction: “l’incise”, which consists in placing between commas an information. This works like parenthesis. So here you could say:

Une amie (elle était venue faire du tourisme à Kyôto) m’a dit qu’elle t’avait vu te soûler à la taverne !

or

Une amie, elle était venue faire du tourisme à Kyôto, m’a dit qu’elle t’avait vu te soûler à la taverne !

As the construction becomes hard to understand, you can remove “elle était” to make it clearer:

Une amie, venue faire du tourisme à Kyôto, m’a dit qu’elle t’avait vu te soûler à la taverne !

And you basically get your first sentence, but with some commas.

Note that if you are writing literature, you can use dashes instead of commas:

Une amie -venue faire du tourisme à Kyôto- m’a dit qu’elle t’avait vu te soûler à la taverne !

There is a subtle difference in meaning between the “proposition subordonnée relative” and “incise” constructions. The first usually is here to raise an ambiguity about what you are talking about (here you say that it’s the friend who was visiting Kyôto, and not the other one visiting Shangaï), whereas the latter is more about giving some new information (here you suppose your interlocutor already know who you are talking about, and you give him the information that this friend was also visiting Kyôto).