Considering she used to be the 3rd espada, she is quite strong. Still, her power is still based on her previous rank, so she is stronger than the previous 4th, 5th, 6th, 7th, 8th and 9th espada, but she is weaker than Baraggan and Starrk. Though she was replaced by Harribel as 3rd espada, we wouldn't know who was stronger unless the two of them fought, which will probably not happen since Aizen killed Harribel.