Tenant who vacated is threatening

Hi,

I have been living with my husband and 2 yr old son in a 3 bed house from June this year. I decided to rent one of the double rooms in my property in August this year.The reason I decided to rent was that my husband usually does night shifts and myself and my son were alone at the property.As I was new to the place,I wanted someone to be there .I rented the double room to a couple. The couple moved in august.The girl is 21 yr old british born asian who was being funded by government for her studies and living.She moved in as it was easier to commute to her college from my place.Her husband was jobless and was full time at my home studying.They lied to me that both were studying and will never be at home.Initially they were ok.But if I told the girl to keep the kitchen tidy or tell her to keep the bathroom clean,she used to get upset and stop talking to me for some days.I only thought it was her immaturity and I used to go up to her and speak.

I went on holiday with my husband to India to meet my parents 3 weeks back. My son caught a serious infection from the flight and was hospitalised in India for some time.As he was unfit to travel back,I left him there.I came back with my husband and the problems started from the next day. She would not clean up the kitchen and when I asked her,she will show her face to me. Usually from then on,she and her husband will be in the house morning till evening. I am an IT professional so I go to work in the morning and come back in the evening.They will leave right before I turn up. I came early from work on Friday and saw them keeping the kitchen unclean.At about 6:30pm, they were going out.Her husband had already told me before that if there were any issues with her,pls tell me and not my wife as she is immature. So on that day when they were going out,I called them and told her husband to clean up everything before they leave.I only requested them and asked them to make sure.She started screaming on top of her voice started abusing me and shouted at me.She then went away with her husband after a half hour long shouting.Her husband came back in 10 mins apologised to me and said she left him.He also told that this has happened when I was on holiday.He states he almost packed his bags and left but then he thought about me and my husband as we are the landlords and that we were on holiday and came back. This guy was in the house for 2 days until sunday.His activities were not great as he brought some one in to the house when I was away.When I asked him for his mum's number he refused to provide.So I asked him to leave immediately.For which he was rude and said he can only vacate the same day evening at 4 and if I didnot agree he will call the police.He did not speak a single word on Friday when his wife was screaming on top of her voice.He then vacated on sunday evening at 4 as me and husband patiently waited for him to leave.The boy when vacated refused to give the letter back to me that stated deposit of 240 will be returned on giving 2 weeks notice. I have not given the deposit back as 2 weeks notice has not been provided.Also it was dealt with his wife, tomorrow she shouldn't come to me and say I split with my husband I dealt with u and that u should not have returned it to him. So I didn't give it to him.This week's rent has automatically come to my account through direct debit.I am willing to cut 2 days as the guy stayed there and give it back but the rent is coming out of the girl's account and have no details and she has ran away.

The problem now is that she is blackmailing me sending text message- This is the message she has sent me.

"If your wondering why i havent asked you for MY money yet.Its because i want u to stop being money minded,bring ur child back to uk and give him good living conditions and feed him properly.When social services find out hes being ill treated in India they will take him away from u.Be careful hes a british citizen.Don't try to challenge me.U will regret."

--- What right she has to talk about my son.My son is with my parents who are looking after him very well. I will be picking him back in a couple of weeks when he feels well.What do I do now?She is highly capable of blackmailing me.My husband works late night shift and I am alone at home.What do I do?Should I respond back or what do I do if she stands before my house one day?Pls advise.Very much affected Upset with such behaviour of tenants.

Thanks
PW