I guess it depends on if you are consulted before she takes these trips, and if you consent to it. You are paying for a service, but one of the major reasons a childminder is different to a nursery, is that they are cared for in a family setting. This means that there are times when the needs of one or other of the children has to come first.
I childmind for 5 children, all on a part time basis, and have two young children and a teenager of my own. There are times when I have to take them places to collect or drop off one of the others, I have taken mindees to the dentist when their parents were both at work, and had to take my children with me, as well as taking my kids to appointments etc bringing mindees with me.
I always check in advance with the parents, and have never yet had an objection, although sometimes parents have rearranged their work (only occasionally possible) to take their kids and one or other of mine so I can take only 1 child to whatever it is.
If you are not happy with it, discuss it with your CM, she may, or may not be able to rearrange things to keep you happy, but equally she may say she will not be able to take your DC if you are unhappy about it. Likewise you can choose to move your DC to another childminder, or to a nursery, whose routine is more to your liking.
I wouldn't say you are unreasonable to be concerned/annoyed about it, but I do think you need to speak to her, not moan about it on a forum.