The Tenacious' clip is quite stiff indeed, as are the metal clips on it's other Chinese-made siblings in the Spyderco line (Ambitious, Persistence, and Resilience). You get a lot of knife for the price, but there are some trade offs.
The best way I've found to tame the fierce (tenacious?) grip of the strong metal clip requires removal of the clip, a hard rubber/plastic tipped mallet, and extreme care. Once off the knife, place the clip on a straight, hard surface so the apex (top part) of the curve is facing up. Tap it with the mallet several times, gently, and replace it on the handle to test your results. If the clip is still to tight, repeat the process as many times as necessary. Patience is critical to avoid overdoing the adjustment, and ending with a clip that doesn't grip at all.
I hope this works for you, and your daughter can enjoy EDC and use of this nifty blade.