Are these really good pants, or are they something you'd be willing to try to hem yourself with a little instruction? It's really not hard - be brave!
If you feel up to it, especially if these are kind of your average khaki type mid-weight, tight weave cottony pants, it's pretty easy and will save you lots of money.
1. Have your daughter try on the pants. Take a piece of ordinary chalk and mark the length you want the pants to be. You don't need to make more than one mark on one pants leg.
2. Take the pants off and measure the distance between the mark and the current bottom hem. Let's say the pants need to be made 3" shorter than they currently are. Just make a chalk mark 3" from the bottom hem all the way around the pants leg. A mark every couple of inches is fine. Do the same for the second pants leg.
3. Just to be sure, pin one pant's leg all the way around at the new level - in this example 3" higher than it originally was - and have your daughter try them on again. If you've gotten the length right, you're in business. If not, just wipe the chalk away and try again.
4. Once you're sure the length is correct, you're ready to make a new hem, and your iron is going to help you do it. Using your chalk marks as your guide, make sure the pins you've placed make the pants leg an even 3" (in this example) higher than it originally was. Iron this new line in place, making sure to turn the fabric under - in other words in the direction of any hem you've ever seen.
5. Now you can take the pins out. Since you're going to need enough material to make a new hem, but you don't want too much excess, measure
2" from the new ironed hemline down toward the old hem. Do this all the way around each pants leg. (In this example, you know you've done it right if you end up with chalk marks around the pants leg 1" above the original hem, and then an ironed line 2" higher than that.)
6. Now it's safe to cut your fabric. Just cut along the chalk line you've made, 2 inches
below the new hem level. If I'm not explaining this clearly enough, just think about what you're trying to do - you need enough material left to make a new hem, so you want to cut below the new hemline, not above it.
7. Once you've cut away the excess fabric, fold your fabric at the new ironed hemline, turn your pants inside out, and pin the new hem in place, placing the pins close to the new hemline, not near the raw edge. Now, because you don't want the top of the hem to be made of a raw edge, measure 1/2 inch from the raw edge, turn it under that amount, and use your iron again to press the hem in place. At this point, even though you haven't sewn it down yet, it will look like a finished hem.
8. Use a few pins to pin the top of the hem all the way around each pant's leg. You won't need the pins at the bottom of the pants leg anymore at this point, so they can be removed.
9. Now just thread a needle with a long piece of thread. If you've ever sewn before, it's customary to use just one strand of thread, leaving a tail you hold in place with your hand as you sew, but if it's easier for you, you can make a knot at the end of the doubled thread and use that. Your pants leg will still be inside out so you can see the edge of the hem. At the top edge of the hem, just make a small stitch (about 1/8") long that will join the hem and the pants leg. The idea is to for only small stitches to show on the outside of the pants. So about every 1/2" all the way around the top of the hem, just make another small stitch joining the hem and the pants leg.
10. As you're sewing, the stitching on inside of the pant's leg will look like this: .__.__.__.__. The outside of the pants leg will look like this: . . . When you've gone all the way around, make 2 or 3 stitches on top of one another, slide the needle under those stitches, then pull the needle through the loop that exists before you pull this stitch tight. That's the final knot.
I know that this is a long explanation, and maybe more than you needed, but I tried to include every step since I don't know if you've ever sewed a stitch.
Hope this helps!