She’s half-lying when she says that she’s just there to “take a look at his eccentric bride”; she’s Oscar’s maternal grandmother, it’s literally her grandson’s marriage. I don’t think that Tinasha knows this because of her wondering about “if witches didn’t intervene”, well, then your hubby wouldn’t be born you baka.

This is likely related to why Lavinia cursed the Farsas’ royal family. Her daughter Rosalia (Oscar’s mother) is dead as the series start; she probably cursed her son-in-law Kevin (Oscar’s father, former king) out of sorrow, or Kevin did some major fuckup when treating his wife.