Unknown boyfriend via FB

[MerryBerry12]

Our dd is 19 with some SEN. Despite our previous conversations and warnings of accepting friend requests from strangers she now has a ‘boyfriend’ whom she does not know.
We check her messages (she knows we do this).
They have met once in a pub.
With some digging around online we know he has been in trouble with the police and has been to court and only just escaped a custodial sentence. She does not know that and we have not talked to her yet about that.

How on earth do we tackle this one without her becoming more and more secretive about relationships in the future?
She is so vulnerable both sexually and emotionally and has previously been the victim of coercion when at school.

omg bless you it must be awful,I worry about my daughter in thay way aswell,it's so worrying this world today,you do right looking through her messages etc with her having sen issues,but she is also 19 so just be careful coz at that age she can just say yano what I'm going and could push her further into this guys arms,just carry on doing what your doing but from afar,try to be nice about it even tho inside your getting chewed up about it,I'm going to be exactly the same with my son aswell as he has alot of sen issues and doesn't like people at all so for someone to take advantage of him would really hurt me probably more than he would get hurt by it if I'm honest,if I had my way I'd never let my kids out the door or talk to anyone now days,too many vulnerable people about that others take advantage of,sorry don't have any answers for you but just know your not alone and your not doing anything wrong your protecting your child which Is your job and your doing it very well by the sound of it,don't give up hun x

Thank you for your response. It's good to know we are no alone xx