No, Gloria de Oliveira is not a goth artist, because they play Ambient/Synthpop/Dream Pop, while goth music consists of Gothic Rock and its derived genres, like Deathrock, Darkwave, Ethereal Wave, and Coldwave.

If you want to dive into the goth music scene, some of the bands that might appeal to you if you enjoy Gloria de Oliveira are Lycia, The Frozen Autumn, and Them Are Us Too.