Interacting

Woman not observing pardah with non mahram males

Q: A woman doesn't observe pardah (covering her face). 

She works in a home. There is a man and a woman. The man observes pardah from her. When she comes to work, she comes walking and without pardah. The employees have tried to encourage her to wear pardah but to no avail. 

Now she is offered a job at another place. There it is not clear who she will come into contact with. 

My question is, if a person suggests for her to take the job, is the person sinful because she will come into contact with men. She isn't observing pardah, she is also leaving the house to come to work, so on the way she is going to come across men.

Keeping a non-mahram as a Facebook friend and conveying salaam to non-mahrams

Q: 

Can I keep a non mahram as a Facebook friend? If I don't talk with them unnecessarily & don't post any photo of mine? Will it be considered as zina for me? Can I give likes to the posts of non mahrams or will it be considered as zina? 

Can I give salam to my non mahram relatives? Will it be considered as zina?

Attending an engagement

Q: I am invited to my 1st cousins engagement. I am the only female in niqaab and I am the only person in my family who is in a Darul Uloom. I don't know if I shouldn't go because I don't want to break the law of Allah Ta'ala or must I go to keep family ties. If I don't go then my family will get really upset with me but doesn't the command of Allah Ta'ala come first?