My first question is: does her hair need trimming? If it isn't being damaged, and it's healthy, then it doesn't need to be trimmed. I don't trim mine because it isn't being damaged, and it's grown down to my hips because of it (so I've gone about 12 years without a trim). If, however, your little one has some damage, you might want to trim about 1/2 inch a month or 1 inch every two months until the damage is gone. Then you can stop. If her hair is uneven, and that's why you want to trim, then you could get away with trimming only when the unevenness is noticeable. The great thing about curly hair is that it takes a while to notice unevenness.

I don't know how curly your daughter's hair is, but you may actually be able to trim it yourself (if you are wanting to remove damage or even up her hair), so long as she always wears it curly (curls are forgiving. Straight hair isn't). You could wet her hair, comb it out with conditioner in it (preferably with a Denman to help form her curls). Then pick up each curl, and hold it firmly between your thumb, ring and pinkie finger, and your pointing and middle finger. This helps stretch out the curl so you can get to it. Then give it a snip, straight across the ends, near the end of the curl, making a "T" between the hair and the scissors. Take off much less than you think you should, because curls shrink up to a fraction of their wet length when dry. It's impressive how much they shrink, so be very careful. Back in the old days when I trimmed my hair, I used to do my hair that way. Lift up curls on either side of her head from time to time to make sure both sides are even. I even would have friends who knew nothing about hair help me, and they did no damage, while salons can do plenty.

I must confess I never had great experiences in the salon, so I tend to like to handle everything with my hair myself. That way I know for sure my hair and I won't get hurt by rough combing. However, if you have a salon you know and like, of course you can have professionals do the trimming.