Having played the games, Xia You actually knew that both Cheryl and Marley were Partner Pokémon Trainers.
There were five of these so-called Partner Pokémon Trainers in the games, male and female, young and old, none of whom knew one another. Simply put, they were companions you could travel and battle alongside.
All five had appeared in the anime as well, and had even spent some time traveling with Ash and his friends.
That was why, although Xia You hadn't realized it immediately upon meeting Marley, he had recognized who she was as their conversation progressed.
But as he had said, games were games, and anime was anime. This was the real world, and he really didn't have the spare energy to look after a companion who was far too young and vulnerable.
More importantly, with Cheryl joining them, his group was already full.
In the end, however, Xia You still took Marley along to Oreburgh City for the time being.
There was no helping it. Neither May nor Cheryl could bear to leave such a little girl here alone. After discussing it with Xia You, they agreed with his wish not to add another companion, but unanimously decided that they could take Marley to Oreburgh City first and then decide whether she would stay or leave.
With Marley joining them, the next stretch of their journey became even livelier.
She seemed to have an endless supply of things to say, her mouth never stopping. First she chatted with Xia You, then May, then Cheryl, before starting over with Xia You again. The cycle repeated, and even when the three had nothing left to say, she could talk to herself for ages.
Clearly, traveling with other people really was a novel experience for her.
No wonder she would become a