I have used tampons for years & know exactly how to do it right.That said, when I am very light in my flow, sometimes it has a bit of friction going in at first/pulling out. (sorry for TMI!)
So if your daughter says it hurts, you might want to pull out a tube of KY jelly & rub a dab onto the tip before she tries to insert it. Additionally, for her to practice a couple of times to get it right, use tampons with a plastic applicator tip (even if going forward you do not want to use those). Easier to slide in & out (& for practice, she won't need to eject it from the applicator each time).
If it's not due to that, but really more about the angle, etc. my mom had me squat a bit off the edge of the bathtub & put the tip in, then while gently pushing "in" wiggling it a bit, forwards, backwards, side to side, to see when it felt like it was going to go in & when it didn't.
It takes a few tries (& discarded tampons!) to get it right. For the purposes of practice, make sure she is using the lightest absorbancy (smallest diameter)
Also, it helps if you "prime" the tampon just a bit by pushing it to the top (w/o pushing it out of the applicator) so that the part being inserted is firmly rounded.
For you to give her great advice, try this visualization:
Picture yourself from the top down like the face of a clock. Your belly button would be 12, your hips 3 & 9, your tailbone 6 o clock. Now, put in a tampon, noting how your body is positioned (if you are sitting, you will insert it w/a different angle than if you are standing or squatting).
As you do this, think about which "time" the applicator tip is being pointed towards as you insert. Also, distance from center. So maybe you point it back to 6, but not at such an angle that you would hit your tailbone, but 1/2 way from straight up & back to 6...
Then, you can have your daughter do the same (same position, insert tip, point to the time, & push inside). You could even take a round piece of cardboard (maybe from a frozen pizza) & draw the clock face on it so that she has a visual in front of her that she can refer to as she does it, because maybe for you it is 1/2 b/t straight up & 6, but for her she will find it is more straight up & more towards 3.
Then she can mark that, & use it for her own reference while she practices some more.
Best of luck!