ditto
magic beans is great, and they keep in stock what's selling - meaning, what people find useful in the area.
If your friend has option to keep stroller safely downstairs, it opens up possibilities. Most popular stroller for newborns in Boston is uppa vista and bugaboo, I'd say. There are a lot of used bugs on our CL. Once the child grows, she has other options. Some people walk everywhere, and use a bob (or similar jogging / all terrain type stroller), and get a lightweight stroller for PT, or traveling. Some only have a lightweight one. Maclarens are extremely popular, even more than g-lite and g-luxe. Baby jogger minis are also used more for older kids, that is my observation.
That's in a nut shell. You can see all kinds of strollers here in Boston. It's fun to stroller watch here!
North Brookline (Coolidge corner area) is similar to Cambridge (in terms of streets, small stores etc, public transportation). South Brookline is more a suburban type of thing, with more driving etc.
HTH