I'm sorry: I didn't intend to single you out with my comments, StarExpat.
I do get cross when people (not just you) try to tell us what we should or should not be charging without looking at the whole picture or considering that another parent's needs are different from theirs.
I was once told by a parent that Mumsnet mums were saying I shouldn't be charging as much as I did. She said a childminder in the next town was shocked I was charging so much.
Yet I knew, from other posts and because I knew her, that she would be charging for meals, overtime, late fees, playgroup fees, outings and a whole lot of extras, all of which are included in my rate. She wouldn't be providing the same level of service as I would, and I knew, because I'd heard her say so, that she refused to work after hours - I often need to have the children very late, even overnight at short notice.
In your own situation, the childminder wouldn't suit. In the OPs situation, she's probably ideal for the hours she works, her flexibility and, because the OP works during holidays, those holidays can be co-ordinated so she isn't paying twice - presumably she, too, takes holiday herself.
A childminder who doesn't work holidays, or who will do a term-time only contract would be fine for you, but not necessarily for the OP.
I just wish people would bear these things in mind before insisting that childminders have no right to charge for their holidays or bank holidays, or higher fees or the many things that some Mumsnetters seem to think are "wrong". Like me, those childminders have probably worked out the rates and charges that work best for them and the clients they hope to attract. We can do that because we're self-employed and don't have to follow everyone else's rules.