I'm far from the perfect person to give advise but I probably would not wish a happy anniversary. It would likely just aggravate Her since she seems to view the marriage as over already.
I know it's difficult with it being your birthday, a male friend assisting her, and her stating her anxiety around you but you need to keep your chin up. Easier said than done but you'll make yourself crazy if you look too much into her relationship with Her friend or her feelings toward you.
When you interact, treat her as an acquaintance. Show kindness and courtesy, but don't ask questions about her life. Even if it's as simple as "how's work going?" -- show ambivalence. Don't acknowledge the anniversary. Don't attempt physical contact and don't ask her feelings or intentions about the marriage. She's probably confused and it may just Smother and pressure Her.
You need to work on yourself, think about yourself, and do what's best for you. Alter your expectations too. Don't expect her to wish you a happy birthday or be happy to see you or speak to you.
