My bf keeps spending time with his ex gf?

My bf keeps spending time with his ex gf even though ive told him i want her completely out of our lives. He assures me they're not romantically involved, but they dated for a long time and he relies on her for advice and support. I think she sneaks around trying to sabotage our relationship. She is clearly still interested in him, and ive told him that but he still stays in touch. I think he should respect my wishes over their friendship and business dealings. Do you think hes subconsciously still interested in her?