It sounds like you're dealing with two issues: 1) Mom doesn't understand the word "no." And 2) Mom wants to be one of the "cool kids" no matter what sort of embarrassment it causes her or you.
Issue 1) Mom doesn't understand the word "no." Sure she does. She just thinks that if she makes enough of an ugly fuss, you'll give in. She knows what she's doing, asking all of these leading questions. Frankly, I would be a little insulted that she doesn't seem to think YOU can figure out what she's doing.
So she doesn't want to hear "no?" Not your problem. She needs to understand that she is not welcome to take pics or videos or whatever she thinks she can do to end up in the same place as the wedding party and make it extremely awkward for the HC not to say, "Why don't you join us, peach's mom?"
Basically, you need to tell her, "Mom, this is a very small wedding.You barely know the HC, who are very private people. They would not be happy if you showed up to take pictures or video from the road." If she screams and cries and carries on, let her. If she's on the phone, hang up. If she does this in person, leave.
Also, make sure that your friends KNOW not to pass info along to your mom, because you would be amazed at the lengths some people will go to get what they want.
But honestly, Issue 1 is just a symptom of Issue 2) She is fixating on the wedding of a couple she doesn't know very well because she wants to be one of the "cool kids." Sometimes, as parents of adult children age, they struggle with the concept of not being the "young" generation anymore. And then, when their child finds a good group of friends involved in a fun activity, they want to be included, because, afterall, that group accepted the adult child, and the parent, in their own mind, is just as cool/fun/important as the child- if not more! This can lead to power struggles with the adult child for the friends' attention, the parent doing things to intentionally embarrass the adult child in order to make themselves seem more important, or just ignoring boundaries, leading to the child leaving the group, just to get away from the dynamic.
We struggle with this with some relatives who were always more "buddies" than parents. They were always the ones hanging out with their kids and the kids' friends, using the excuse that if their kids were going to party, they would want to be there to "supervise" and make sure the kids are safe. The end result was that no one in the family trusted them with their kids, because we'd seen how they "supervised" their kids. And now that the kids are grown, the parents are still hanging out with the kids and their friends. And because the parents tend to revert back to some pretty silly behavior to fit in with the kids' friends, it's pretty unpleasant for everybody.
And when the family gathers, the aunt and uncle glom on to their kids and us cousins, which changes the group dynamic and can make things sort of awkward. It's like they're so afraid of being left out or being seen as "old and boring," that they're willing to alienate their kids and insult their peer group (by calling the other aunts and uncles "old and boring") and generally make fools of themselves.
The kids haven't figured out how to handle it beyond staying completely mum about any plans they have with friends, avoiding posting pics or info about any plans with friends to facebook, even after the fact, and telling their friends not to mention plans or gatherings if they happen to see the parents at the grocery store or something.
PS, why does she have items "that she's not supposed to have" at her house?