Even if there were connections to the underworld to track down sold slaves, the chances of finding her mother or both of her parents was very low.
If they had been treated poorly then they will already be dead or in a condition where they would rather die than continue living.
Even if the current owner was found, Monera would have to risk going against that owner who is probably a noble or king of a country just to try saving them or to avenge their deaths or suffering.
The vengeance would not stop there as there would be the previous slave owners, the slave dealers and those who captured them, who are responsible for her parents misfortune resulting in a lot of bloodshed because of the pursuit of revenge for the loss of her parents.
Of course this was just hypothetical, it depended on Moner's current outlook on humans and how she chose to act from now on and the consequences involved.
Currently Jinbe is a warlord of the sea and has formed a deal with the World Government so if she did act against others, his image and the trust in the Fishmen would be damaged and go against her mothers original dream.
However there was a more frightening possibility that would not be known to the Fishmen and Merfolk until later.
The murder of Queen Otohime was not done by humans but instead by Hody Jones a fellow Fishmen, those loyalists to Queen Otohime who continued to keep her dream alive and took positive action would be like a stain in his eyes.
Since they were fewer in number and unprotected when going out to rescue drowning people at sea, they became easy targets for elimination and Monera's mother was one of them.
Monera's story also had some hints of being consumed by hatred which suggested that she may have been hanging around with a bad crowd back then and acting rebellious after losing her mother, it was almost like she had become a target by the New Fishmen Pirates and was being influenced by them.
Either her father noticed the unusual circumstances surrounding his wife's disappearance or the influence his daughter was under which may have lead him to investigate further on his own resulting in his death many years later or he had ventured out and met a tragic fate at sea being captured or killed.
Alyssia did not dwell on the subject for too long since she was still quite drunk and sleepy so she lied back down and fell asleep.
During the talk between Monera and Liushi, she had been in a very light sleep so she woke up and heard what they had said but pretended to be asleep and not interrupt them to gain some information.
Although some parts were vague and not too detailed, as a reader of One Piece she was able to know some things others did not and put together the information in a way that many would not have thought of.
Another day had passed by with Tristan, Liushi and Monera getting into the finals and the next day there would be more battles to come.
Alyssia woke up from her deep sleep near her two friends who were still cuddled up and cursed. "I need a god damned hangover cure..."
The stinging pain on her head along with the slight sickly feeling was awful for her body which did not have that great of an alcohol tolerance and she missed good old prescription tablets or pills!
Although there were some concoctions within the world prescribed by doctors, they were often stingy with passing out their recipes and only usually provided them to critical patients or rich people who could pay for it.
Her eyes turned to Tristan as if she saw gold coins. 'Perhaps... she can do it. Or at least something similar.'
Cheaper medicines, tablets and pills that could be distributed and sold to fight off cold, flu, inflammation, infection, body pain and other types of problems in areas where they would be in higher demand or spread of illness.
The more effective they are, the more they would be purchased by those in need of them.
Alyssia looked at Tristan's sleeping face and grinned. 'Well... she already has some other projects but this could be a quicker way to earn some berries on the side to support her current projects.'