Having been a guide myself I went on a few camps, none more than an hour or so from home, and I had an absolute riot!
I honestly appreciate your reasons for wanting her with you while you go away, but try and look at it another way. She will be supervised and with her friends learning stuff (I still say I learned more from guides than school) and if anything does go wrong your parents are nearby.
Anyway, she may hate her first week and not want to go for the second camp, or your holiday itinerary may be so brilliant she decides not to go anyway.
If she's in Guides then she must be at least 11, so give her a chance to make a choice.
I don't know if she is your only child or if you have more.
If she is an only one then grab the opportunity to have a child free holiday.
If you have other children, then it might be difficult to leave one behind, but it is only a week.
When I went to guide camp there was no such thing as a mobile phone. I walked nearly a mile to the phone box to ring my mum to say I was alright (and reversed the charges ) You can have a direct line to the guiders and your daughter.
I really don't think you are being silly. You are only worrying as a responsible parent would.
But If she really wants to go on the camp and you insist she comes with you, are you prepared for the week long sulk?