Hi, 13lucky, it'll be fine !
Do tell your DD that she is going to have jabs tomorrow, don't make a big deal out of it, but tell her.
Do NOT let her feel your anxiety, she will pick up on it and believe there is something to worry about and then get more anxious is anticipation herself which will lead to a more dramatic response which will confirm to you that it was awful which will make you dread even more the next time she needs anything doing (travel vacc, stitche, who knows?)
Do tell her it is going to be 2 little scratches or some such phrase that acknowledges that it hurts (it does!) but doesn't overstate how bad it is (as it is not that horrible)
Do tell her it is to help her not become ill. If she has had any recent episode of illness (a cold, tummy upset, chicken pox, anything really) use that to remind her how unpleasant it is to be ill and how worth it is to have '2 little scratches' to try and prevent illness.
Use bribery and rewards liberally - chocolate buttons and comic from newsagent was what I used with mine.
And do breathe!! Worse things happen at sea .
Oh, and HVs are usually v good at doing vaccinations quickly and with maximum distraction. Yes, she is likely to mind the second one more, but she will be fine.
Oh, and do make a big fuss about how Brave she had been (even when she wasn't!) and what A Big Girl she was now.
Do not NOT TELL her what she is going to the doctor's surgery for - it is awful and makes it harder for the children. And IMO gives them grounds to not trust their parent...
Good luck tomorrow .