Look, there's age gaps and then there's AGE GAPS, and the sliding time-scale DOES exist, but you know what else exists? A story about Nekra's teenage daughter (older teenager, at least sixteen or so) written in 2009, a year before Oya debuted at the canonical age of 14.
Like, there is NO way to make someone who had a teenage daughter around or even BEFORE the other one became a teenager herself, like....into a viable ship. The sliding timescale can not change the fact that Nekra was a full grown adult woman for decades before Oya debuted as a teenager.
They work perfectly as a surrogate mother/daughter relationship or even big sister/little sister, but if you want to explore them in same gender relationships, there are plenty of other options. Maybe Carmen Cruz aka Gimmick, the shapeshifter from Children of the Atom breaks up with her girlfriend and she and Oya date, and random thought but now I'm thinking of the possibilities of Nekra having a relationship with Jessie Drake, who is trans and same-gender attracted (can't remember what she identifies as specifically). But Jessie's explicitly said she's not interested in moving to Krakoa, she and Nekra could have some things to talk about and see what happens. Or maybe Tempo and Theia don't work out, Heather and Nekra could be an interesting ship, etc, etc.
There are options, we don't need Oya dating a woman old enough to have a daughter older than Oya by the time Oya was 14.