Op I have been through what you are going through now. I really, really sympathise as it is hellish while you are on the receiving end. I had the sneering too. It's getting better now that my DD is an older teenager. Hold on to the fact that things will improve.
It's very hard but you need to try and not take it personally but it really got me down until I was considering ADs. Don't let it get to that point! Do everything you can to be busy with your own projects and hobbies. Do things to make yourself feel happy and fulfilled and get some rl support from friends and family. Be less available to her, while keeping the lines of communication open to her for the important stuff.
Her teenage urge is to break herself off from you and to individuate herself. And to have more freedom and independence. But she may not feel entirely confident about that yet and she is very like you, and of course she loves you and you are close, so she basically has a need to be horrible to you and to reject you in order to move on if that makes sense! But she still needs you there in the background as security!
And of course for someone wishing to be free and independent, a holiday with mum when you are together all day every day is going to exacerbate this issue. Next time I would go with a mix of friends maybe of your age and hers?
I suggest you read Untangled by Lisa Damour.
And listen to two of Susie Orbach's podcasts on BBC1 concerning Amelia and Grace (there are two episodes).
www.bbc.co.uk/programmes/b07v33xy
She doesn't deal with the vile behaviour and the sneering from the teen and how that makes us as mothers feel but she does deal with how the teen is feeling, which is interesting.
Good luck and don't forget that just by being there and being a solid, consistent presence in her life, you are doing her the world of good. It can be an utterly thankless task at this age but it does get better I promise!