thanks for sharing this example, which is very interesting. I’m not saying that adding English as a third language can’t work, but I think your friend is quite exceptional in sticking to the method she chose. Anything can be done if one is sufficiently motivated, but when parents are confused about what to do and struggle to find the right approach for two languages, I really don’t think they need to worry about English as a third language.
That said, if they really want to and are clear about how to, why not?
By the way, I’d really love to hear your friend’s experience, why don’t you invite her to join the discussion?
Thanks,
L.

Well I just met a friend yesterday who speaks spanish to her child as she is from Mexico but as she knows English she lived in new York and studied at University there. She has decided to teach english too and she has a set time in the evening from 8 until he goes to bed when she peaks english. The child goes to school in the morning therefore gets plenty of Italian and the father only speaks Italian. the child understands and speaks all three languages and he is 5 years old.