Friendship does not change the rules of Islam as far as Mahram and non Mahram.. Friendship between families must remain in the frame of Islamic rules. Man can not freely chat with his friends wife, nor his wife can freely chat with his friend. Full Hijab must be practiced between men and women because they are in fact non Mahram despite the friendship between the families.
We have come across many unwanted situations in families because of non obedience of Islamic rules when they mix with other families and friends. In some cases, families were destroyed because of that.
The only way to save ourselves and our families is to abide t the teachings of Ahlul Bayt (AS).