Well, if your sister is moving in with you, then I'd think she can just get used to violin practice, since I am sure there will be enough things you will have to get used to for her.  LOL

Good to hear that the lesson went well, and I repeat that I think you have the song down well and the recital has every chance of going well.

I figure it is a good time to bring up the topic of barfing.  LOL

Well, if not actual vomiting, we're also talking about assorted tummy upset that can be an unpleasant distraction during performances.  But even actual barfing isn't all that uncommon, and some famous musicians have had plenty of problems with it, so it might be good to give some pointers.

Obviously it is best to eat light on the day before the performance, but you *should* eat.  I recommend a small meal with some high protein food in it about 2 hrs before you have to leave to go to the recital.  Meat, nuts, cheese, anything like that.  Protein takes some time to digest fully and will help keep you from feeling hungry, but since it does digest slow it will also help keep your sugar curve stabilized.

The sugar curve is important, since if it goes too low or too high it can make it harder to play well.  It is your body's energy, and you want it to stay steady for the performance.  If it is low, you'll feel more tired and forgetful, and if it is high it can make jitters worse and add to nausea or cramping.  Also, if it goes high, the "drop" can make you feel dumber and clumsier than usual real fast. 

So avoid sugar/candy right before going onstage.  Stick to drinking just water for the hour before your performance.  Try to taper off on even the water as it gets close to time to perform.  The less that is in your stomach, the less there is to barf and the less chance of barfing or other tummy upset.  To cope with possible dry mouth from nerves, consider getting some sugar free breath mints or small sugarless hard candy. 

Nerves will likely be at their worst right before you get to go onstage.  If you are standing backstage with the other people you are performing with, a useful trick is to make sure *they* are ok.  Quickest way to forget your own jitters for a moment is to help someone else with theirs.

Once the performance is actually underway, it will be over much faster than you may think.  The actual time onstage tends to go really quick.

Afterwards, though, you will have adrenaline still running crazy and probably a bit of let-down.  For all that you are worrying now, within a minute or two of taking your bows and leaving the stage, you are likely to find yourself thinking "is that all there is?"   That may seem impossible to you right now, but I assure you it can happen.  Especially with such a short performance time after all this preparation, I would say it is even more likely.  Have a nice dinner planned for afterwards, maybe a fave desert, a few drinks if you are so inclined.  After the show, celebrating a little to "break training" can help with getting over any post-gig let down. 

Due to adrenaline and general excitement, you also may not sleep well.  So if you have to work the morning after, figure it may not be one of your all-time best days.

I don't know if any of this will be useful for you, but it's just stuff I learned over the years and used for coping with pre-gig jitters, stage-fright and aftermath.  I've always been prone to stage-fright.  I didn't let it stop me, I just learned to cope with it and even maybe get it to work for me a bit.