do you have a mekor for how old Tzipporah was (saying she tended her father’s sheep doesn’t prove anything)
Since shepherdesses of 80 years of age are extremely rare (to say the least), I’d say the burden of proof is on you to say that she was so than on anyone else to say that she wasn’t.
IOW, where’s your makor that Tzipporah was anything other than a young woman?
The Wolf