I am feeling sick and conflicted. Advice would be much appreciated. It's long because I need to get it down.
CONTEXT
DD is 18 and at Uni.
She has been invited to Mexico with her BF (of two years) and family over Easter. She has to pay flights and spending but food and accom is covered. She is beside herself with excitement and they have been planning for months. She has found leaving home/starting Uni really hard - and has had a few really tough years emotionally - this trip means everything to her.
She has two jobs - one where we live which she does out of term time and one in her Uni city. She works really hard and is working hard at her studies.
For Christmas DH was going to cover the cost of the flight so that her savings were all spending money. That was her present - apart from a couple of tiny things - that's it. He has talked this through with her and she was thrilled.
DD and DH have a very volatile relationship. Both really hot headed and both do and say things that cross lines. DH has worked really hard in the last few years to be more emotionally intelligent in his reactions and is much less explosive than he used to be. The shouting outbursts are now only after a great deal of provocation and he is far more measured. I will caveat this by saying he wasn't always and certainly some of DDs rage is learned behaviour. DS and DD2 are not like this though. Separately to this, DD has also what i would consider real lows - possibly depression. She has self harmed in the past.
We have all (including DD) wondered if there is something going on with DD's inability to regulate her rage. As I mention - some may be learned behaviour, but her rage is far in excess of anything she has seen in DH and far in excess of anything remotely proportional to situations. She will scream, smash stuff, lash out physically, block doorways saying the most disgusting and hurtful things she can and saying things like "hit me then so I can call the police" (noone is going to be hitting her). This can go on for hours. We have talked as a family, tried going through school, were on wait lists for CAHMS (now too old) and she has spoken to a GP who could only offer her low level anti-Ds as wait lists for accessing any talking therapies were insane (she is on wait lists). She is awaiting blood tests for possible PCOS which I understand can affect mood - just thought I'd mention that too. I paid for a few private therapy sessions but she didn't think they were helping, she has tried doing books on CBT to get a grip on her rage, but one tiny trigger - her BF not wanting to come round one evening/someone commenting on her clothes - can unleash a whirlwind of anger which is directed mostly at DH and I. Really spiteful, awful things and occasionally, physical shoving. On a few occasions she has hit DH.
At other times she is wonderful. Hard working/kind/funny/affectionate/self-deprecation etc etc. It's completely unpredictable.
SITUATION
She has been home from Uni for a few days - it's been really calm and lovely. The day before yesterday, she had an argument with her BF. It was on the phone and loud and DH asked her to keep it down as he was on a work call. She didn't moderate and was screaming and calling BF names. At the end of the call DH knocked and went to see if she was ok and she shoved the door shut in his face. He tried again later (a bit annoying when you want to be left but well intentioned) and she was vile to him. This escalated into a massive row and she stormed out.
They avoided each other that evening and yesterday morning she went upstairs to our bedroom. I was downstairs so don't know exactly how the row played out but before long they were screaming and yelling and I know she must have been pretty awful for DH to lose his shit with her.
They came downstairs and she was blocking the door when he had to make a work call demanding that he 'retract' something he had said (about her BF - but fairly innocuous). He refused to retract and told her he would not be dictated to. She started saying really nasty things to get a rise out of him and eventually he (verbally) lashed out at her and she got in his face and started poking him really hard in the chest. Both yelling. Me and siblings asking then to stop but if felt like a volcano finally erupting. She started hitting, kicking and scratching him and so I tried to get between them and she smacked me in the head. DH then held her (hard) to restrain her - she kicked him in the balls and DH lost it and slapped her across the shoulder and face (flat hand if that matters).
It was all horrific.
He told her to leave and she went to her boyfriends house.
He has now said she is not going to Mexico and that if she tries to pay for it herself, he will stop paying her Uni allowance (which she needs to bridge her rent costs) so she can't do afford to pay both.
Even though I feel we have reached a crossroads and something needs to happen, I think taking her one beacon of hope away, might not be the right thing. DH says it's exactly the thing she needs - consequences that hurt.
I don't know if my reluctance is because I know it will ruin Christmas. She has no presents, she will be distraught, the atmosphere will be awful for everyone - especially siblings and it will also ruin her boyfriend's christmas. Or if I just don't think taking away this one thing is too unkind. I also feel that her behaviour stems from more than just being 'horrible' - and if there is something going on, should we be punishing her? DH agrees that there may well be something going on, but that she is manipulative and spiteful at times and that no matter what, being physical is crossing a line (as are some of the horrendous things she said that I can't even bring myself to write).
DH is actually more heartbroken than angry (but also angry) and is standing firm - no trip. And I just don't know how I feel. I don't know whether to go into battle for her or stand with him. It's making me feel sick. I can't bring myself to wrap anything or do anything because I am so sure Christmas is ruined. And of course, on top of that - and more importantly - we have a real problem to resolve as a family which just feels overwhelming and insurmountable. I don't know how I feel about DH slapping her either.
My head is a mess and I can't stop crying. The big picture is how we move forward with and for DD and as a family, but i feel like if at least I could get Christmas clear in my mind, I could face the bigger and more important issues.
Advice please.