How Marla gets Tyler’s house number isn’t explained, as Palahniuk drops more hints about Tyler’s true nature.
Marla, it’s shown, has continued to flirt with death, hurting herself by overdosing (on Xanax, we’ll later learn).
The passage also reminds us that Marla is, supposedly, to blame for “all of this.” We still don’t know how, which makes the Narrator’s apparent willingness to let Marla die seem pointlessly cruel.