None of us wants to be at any of these functions but its inevitable.  I hated seeing our late BM on any occasion.  But, the good thing about a specific event is, we can prepare.  So, I always made sure I looked my absolute best, that's #1.  Then, #2, I tried to be civil and polite.  Now that she's gone, I have a feeling BM dreaded these events, too.  But, if you can manage it, "civil and polite" is the way to go.  It's best for the SKs and gkids.

You'll probably need to get over it for some occasions - weddings, graduations, funerals - stuff there's only one of.  Be civil but don't linger near her.  But you do not need to spend birthdays, holidays and the like with BM. I told DH very early in our relationship that I was not going to do joint birthday parties, go trick or treating with BM, or spend Christmas or any other holiday with BM or her family. If we go to a school event or a sporting event, I feel free to sit far from BM.  She's actually not a bad person, and she's a good mother to the skids, but I have enough reminders of her existence and the fact she was once married to my DH, and I feel no need to see her or spend time with her. 

With my Mr's ex, we pretended we had never met each other. that was fine by me and since his son graduated HS we haven't been in the same zip code as far as I know. My ex and his wife? We are polite. We have to be, we share a grandkiddo and my son is married so we all were involved but it's not a "friends" situation, it's a polite strangers toleration. 

Except at milestone events IF you have a decent relationship with the person hosting (a parent of a grandchild) or the person it's for. If the relationship is not there or you don't feel welcome do have a conversation with your partner and explain how you feel. I would leave it optional on your attendance but wouldn't prevent him from going. Mine does and hates it lol. In my situation it was every get  together, Birthday,  Holliday, bbq etc  and special event BM was included and usually invited with zero regard for us. DH attempted explaining/reasoning with his kids but they refused to budge so we stopped attending. As others said certain milestone events you should try to suck it up and go IF you have a decent relationship with the skids. 

Just the opposite.

Go to every event. Be radiant. Glow your happiness together with your SO.  Rock a hot dress, amazing shoes, a classy makeover, a beautiful hair style, classy jewelry, a luscious high end scent, and dare anyone to say a word.

Occassionally laugh at something SO says, whisper sexy nothings in his ear to keep anyone and everyone present guessing.

Radiance sends the cockroaches scurrying for a dark corner.  Just like a bright light does when it is thrown on in a roach filled room. If the roaches creep back out and attempt to snark out, be ready with a dismissive laugh, a sticky sweet "Well bless your sweet little heart", and a challenging look to let them know that if they escalate, you will happily bare their ass in front of everyone.

Never let the shit stains keep you away.  Wrinkle your nose at them and put your living well on full display with your SO.

Living well is the best revenge. Enjoy living it.

This also ends the Birthdays party's type of events.  Nobody wants to spend time with SO ex. Only weddings , graduation, type of events are ok.  Sporting events type of things. You go but stay away from the ex.   Your SO divorced this ended there happy family 

For the first several years of our relationship DH and BM had extremely little contact, so when things changed I was caught off guard.  It's not something I was prepared for or eased into. 

I'd absolutely insist on boundaries.  Polite acknowledgement in the vein of "hello, nice to see you" and keep it moving is what I'd hope for.  Set a precedent for not sitting near BM and generally limiting contact whenever possible. 

Rags has the best advice here.  Look your absolute best! Glam up and put happiness on high beam to ward them off!

I would get professional blow dry & makeup done, nails polished, great outfit and pull on some Spanx!  Be Classy, Sassy and look Bad Assy!

At first I was cool with meeting the bm at functions but then I changed my mind when I realized how much of a lazy manipulative c*nt she is, didn't want me around her kids (cool I don't want them in my space nor do I want to do your job for you when you're getting paid CS for taking care of them), conveniently pushes her kids off every chance she gets in efforts to make her kids the center of the house I pay bills in. 
 

Im not interested in meeting her, seeing her, etc. anymore so I intentionally avoid events she is attending. Nor do I want to feed my soon to be ex's ego by providing him with arm candy to make his ex jealous. I'm conveniently working during all these events so I can get some semblance of peace without being part of their drama. 
 

Yes a bit petty but I'm tired of that woman (and tired of him enabling her shitty behavior) and I'm tired of being the bigger person. 
 

but really if you have a good relationship with your spouse and your step kids, then yes muster up the strength to attend events for the kids knowing the ex might be there