Your friend has lived with the man in a live in relationship for a few years, so it is not a few weekends' affair. The important thing is to establish that people around them have known them to be living together all these years in the nature of marital relationship.
Now apply other parameters of the SC judgement quoted here by Advocate Kal Jacob and see if your friend is eligible for protection and maintenance order.
If yes, then under DV act she can secure maintenance, child support, child custody and protection order, as DV act protects women in live- in relationship also.
Go through the Protection of women from Domestic Violence Act 2005, and most importantly ask your friend to engage a very capable advocate.