I did some quick googling for "Swedish irregular verbs" and found this useful list: https://en.wikibooks.org/wiki/Swedish/List_of_strong_and_irregular_verbs
Let me see if I understand correctly the distinction between "få" vs "skaffa (sig)".
"Hon fick en ny telefon." then cannot mean that she went out and bought a new telephone, because that would be "Hon skaffade (sig) en ny telefon". Is that right? In the former case, though, she might have gotten the new telephone as a present, or if the telephone company (or the landlord) provided it for her to use.
On the other hand, might it also be appropriate to say "Hon fick en ny telefon" simply from observing a new telephone in her apartment, with no assumption or representation on how that telephone came about?
Your first example is totally correct. If Hon fick en ny telefon, she may have asked the phone company to send her a replacement phone, but she didn't just order a phone or go to the store and buy it with no complications. (Another possible scenario could be that there were only 200 phones for sale and 500 people were queuing to get one, then you could say hon fick en). fick could also refer to just 'received' as in 'it arrived for her by mail'. So Hon fick sin nya telefon i dag works for that scenario.
In the second case, if you see a new phone in her apartment: since this is a result we're noticing, we'd want to say Hon har fått (en) ny telefon. It could be used neutrally as you say but it might still sound like she probably didn't get it for herself. The most neutral way of saying it would just be to say Hon har en ny telefon where there would definitely be no assumption about how it happened.
tl;dr; you're right :)