Kid Chi-Chi was already naturally strong considering how easily she handled that T-rex . Yamcha and Puar comment that she was strong for being able to kill it despite being scared rather than the helmet itself being deadly making it clear that a normal girl her age wouldn't be able to replicate the same feats.
At the same time, we don't know if Gyumao started training her at this point outside maybe the basics (she can fight in anime filler tho).
She was probably slightly stronger than Krillin was before training under Muten Roshi, but probably much weaker than Goku and Yamcha in the first arc.
The fact she went from that to being able to keep up with a heavily suppressed Weighted Goku (the same Goku who no saled an improved Chapa-o out for revenge in the Preliminary rounds) in just 7 years and with seemingly no other motive than to impress Goku, indicates her potential is exceptionally high for an Earthling.
The only Earthling who's shown greater leaps in power is Yajirobe, who is the laziest fighter of all.
