I actually kinda disagree here; if the purpose is just learning, the cortex system is equal to or better than v5 in most areas imo, and keeping with cortex would avoid the added expense of new electronics. However, one of the bigger drawbacks to staying with cortex would probably be the concern that support for robotC (the programming platform used with the system) and continued availability of sensors, batteries, and the like. Because of this, I could 100% understand why someone would still elect to go with the newer system.
Secondly, while the op obviously knows their daughter better than any of us here, my personal advice would be to first let her modify the clawbot to do certain tasks or work better. After this, she could try her hand at building a bot from scratch (perhaps with guidance from op and others). The result will probably be flawed in many ways, but that’s ok. “Failure” is what allows us to learn the fastest. I assure you, my first robot and the first robot of basically everyone in vex was miles away from the complex, thoughtfully designed, and well-built machines you see posted online.
Edit: I started in iq, and would still say that it’s the best product and program vex has to offer. Depending on your daughter’s age, this would be a terrific option, as kmmohn mentioned. If she really enjoys this kind of stuff, you could even consider encouraging her school to start a robotics club or start your own private vex iq team.