Opening wedding presents with mom

I've never heard of this etiquette-wise. Gifts are intended for the couple and it's no one else's business other than the receivers. Maybe it's a tradition thing in your circles but traditions are optional, not required. If you don't want your Mom there, offer other mother/ daughter activity and time.

Did you not have a bridal shower?

She made that rule up. Depending on what type of person she is, she either wants to be there so she can help you start thank-you notes, or to judge and gossip about what people got you. You don't have to do this unless you really want to.

Are you marrying your mother or your partner? She doesn’t get to open anything for or with you. Did you not have a bridal shower? She made up that rule and needs to back off and you need to establish and maintain firm boundaries so that this behavior doesn’t continue after the wedding. It sounds like she has potential and intent to kick them out of their house to become them because she has abandonment/codependency issues that need to be addressed with a therapist.

I’ve never heard of this. My husband and I opened presents in our apartment, alone, the day after the wedding. I’m not sure it’s typically a group activity. The only exception is when opening presents during the bridal shower.

I've never heard of opening wedding gifts together with friends or parents. In particular, it's none of your friend's business what people gave you for your wedding and I can understand your mother objecting to that part of it when your sister was married.

What's not uncommon in my experience is to share what was received from a friend or relative of the parents when they go to the wedding of that person's child, so they can, in their view, gift accordingly. Of course that's also none of their business, but parents sometimes do feel they have a stake in terms of not offending when it's their turn.

Gifts are not tit for tat, and shouldn't be, but unfortunately, that's human nature. Properly, gifts should come from the heart and be based on budget and relationship. It's up to you whether or not you choose to indulge a parental request like this, consider it unreasonable, or give a ballpark idea within immediate family.

We opened our gifts up the day after the wedding with both sets of parents there. It seemed like a nice continuation of the wedding to have family there.

That’s not a thing. The gifts are for you and your fiance, and so the two of you are the only ones who need to be there to open them! Other than gifts opened at a shower, I’ve never heard of opening gifts with anyone but the recipients.