I'm sorry if my original post was disrespectful to interpreters, that wasn't my intention. I have worked with interpreters and absolutely respect their role. I was speaking from my own experience that language line often works better in labour and birth.
Our hospital's interpreter service is for the whole hospital not just maternity, and even though we can request a woman interpreter, that unfortunately cannot be guaranteed. There is one language in particular where usually only a man is available, in my experience women are more likely to refuse a male interpreter than a female one (though I've seen female interpreters refused too). This is mainly what I was thinking of when I mentioned a stranger entering the birth space.
Labour can also be fast moving and an unbooked translator can take a while to arrive, or may not be available at all, which I believe is another reason why language line is preferentially used during labour on my unit.
I stand by my assertion that the birth space should be protected, even from professionals. In my experience, midwives and doulas are often more tuned into doing this compared to other professionals who might have reason to enter it.
Anyway, by the sound of it OP's friend has some sort of interpretation service sorted out, hopefully her hospital is equipped to offer her every option available 👍