It highly depends on gestation, weight, general health and also the season.

With Brendan, 30+1 1545grams, we were advised to avoid public places until at the very least he reached his due date but even then we were told to avoid major shopping centres ect... quite easy when you live in the middle of nowhere our towns pop was approx 50 and thats spread across quite a few farms!! He was a very sick newborn, with several infections, crappy lungs ect. He spent 2-3 weeks in ICU 3-4 weeks in SC and came home at 5w6d, 4w before his dute date. He came home in April.

With Tristan, 34+3 3090 grams, we werent told anything. But he was a very healthy 34 weeker only needing breathing assistance for approx 8 hours. He had no issues at all apart from Jaundice and getting his sucking under control. 1 day in ICU, 5 in SC and 2 on a general ward in my local regional hospital home on day 8, 4w2d before his due date. He was released in June

All the best to your friend, if she does decide to venture out just make sure no-one is touching ect. It's all basically common sense.