Definitely not a smart move; he's allowed to have friends and a life outside of you. So what if he's friends with this person? Unfortunately whatever your feelings towards her may be, he might find her delightful company and good friend. It's not our place to deny others that happiness just because of our own experiences.

I would suggest you seek out therapy if you're not already and learn of better ways to cope with what you rightly call your jealousy issues. All the best.