The Gender of Serena's Sylveon

So recently there's been some decent topic of discussion surrounding the gender of Serena's Sylveon due to the fact that in JN105, the flashbacks showing it as en Eevee give it the tail markings of a male, and in gen 8, female Eevee are given heart shaped tail markings. This has led some people, including to some extent myself, to suspect that Serena's Sylveon is male since the Pokemon's gender ratio is 87.5% male, and only 12.5% female. However, some people state that the production team confirmed it to be female despite this discrepancy, so I was curious if you know of any official sources that conclusively confirm it female.