Arision, I do recommend before/after this gym battle you take a break from progressing in the storyline and try to catch/train some mons up. You're lacking in backups to use as well as team variety, which is essential for Reborn. Also, make sure your mons aren't underleveled/overleveled as that will be a handicap to you. You generally want to keep them a couple of levels under the level cap, which should be around 45 for Aya I think.
Anyways, get rid of Grimer and Dusclops as they won't be doing as much (Dusclops can take on Gengar but still won't be helpful in the double battle). Then, try to pickup any of the following mons: Meowstic, Malamar, Graveler, Piloswine, Dugtrio, Seismitoad, Marowak, Whiscash, and Gastrodon. Be wary of her Gengar w/ Giga Drain and Tentracruel.