for me, titania took a couple tries to perfect a strategy, but the way i won was using a bulk up blaziken!
i know it seems weird, but you can really set up a few against her scizor as it tends to spam bullet punch. just use a couple potions as necessary because it still hits relatively hard, but after awhile, it can sweep.
one thing i would try to watch out for is that you avoid getting her excadrill out while the sand is up, or before your blaziken has a large amount of speed boosts under its belt.
if you're looking for helpful pokemon to add, there's honedge at the top of mirage tower that does really well since it benefits from the field effects. the con is that i believe it comes at elvel 30, and you should probably ev train it, so it might be a bit time consuming.