What is the purpose of
已 in the following sentence？
The English translation given is:
It looks as if she's gone away for a few days.
Or is this an incorrect-character, supposed to be something else?
Here 已 has the same meaning as 已经 and means already. When speaking one would normally use 已经, but in written documents 已 can be found.
I would translate 好像她已出去好几天了 as "It seems she's already been gone for some days".
已=已经. It just represents the past perfect tense. I think [been] is necessary here. The sentence implies that the subject never came back during the few days, in this case past perfect tense is appropriate.
Indeed "It looks as if she's gone away for a few days" is an incorrect translation.
I would translate this as "It seems she's already been gone for quite a few days".
If the 已 were excluded, I would translate it as "It seems she's been gone for quite a few days."
So the 已 emphasizes the passage of time, just like "already" in English.