I've seen a lot of people talking up Martinez but I don't really understand it, she's been beating up waitresses and domestic cleaners in the Argentine regionals, which doesn't really give a lot to go on in assessing her level. Only one of her opponents has a winning record (Juarez) but she doesn't look any good either. Martinez seems to be a TKD fighter who throws a lot of flashy kicks, the kind you learn the hard way not to do once you step up in competition in North America. Her grappling seems concerning (as you might expect from a regional WMMA striker) - in the Juarez fight she tried a TD but ended up pulling mount on herself, and later almost got armbarred; in her ammy loss (2 years ago) she was easily armbarred by a scrub. She's only just turned 20 which is great for 'future potential' but not so great for future experience in the here-and-now against her first real live opponent.
Hernandez OTOH has a solid boxing base (trained with Mexican Olympic team) and seems to have made good progress at MMA training at a top gym (MMA Lab). She beat the shit out of Bryan Camozzi's wife (that practically counts as a win over a UFC vet right?

) and her last fight a good test against Jorand who is another young fighter who moved to the US to improve at MMA recently and has some notable kickboxing titles (probably will be a UFC cantender in a few years herself). Jorand is probably better than Martinez right now IMO but Hernandez was able to hang on the feet while ultimately winning with top control time (one round off a decent double leg, the other off a knockdown). She also showed classic Messican toughness (ate a few hard shots and never flinched). The only big issue I see is Hernandez might not be hard to take down herself. To me Hernandez looks like a good underdog bet as the fighter with better experience, noticably bigger, likely has a more well rounded skillset, training at a top 'murican gym vs the untested Argie cancrusher stepping out of her tiny pool for the first time.