AITA? MIL wants to take friends on family vacation.

Each year, my wife and I rent a large beach house and invite along family for a vacation getaway. We're spending about the same as we would on a two-person international vacation; with the added benefit that we get to share it with our mothers. I also invite a close friend of mine who is more or less family at this point. This year, some additional family from my side are attending.

Over the last couple years, MIL has become increasingly vocal about wanting to invite a couple that she and her partner are friends with. We do not know these people. More importantly, my wife seems worried that this will detract from quality time with her mother. I'm told she voiced this to her mother weeks ago, and we thought that was the end of it.

However yesterday it came up again. My wife is distraught that her mother is pressing it, and I'm increasingly perturbed with this insistence of inviting someone that we don't even know on a vacation that we're paying for. I can tell that the guilt trip is having an effect on my wife, but in my mind she made her decision when she put this to rest with her mother weeks ago - that she wants to keep that time within the family.

My instinct is to reach out to MIL directly and tell her in a straightforward way, "No."

What say you, Reddit? AITA?

Edit: I'm very grateful to you all for sharing your insights. My takeaways at this point are:

• Stay out of it until asked to do otherwise - Let wife sort it out with her mother unless I am asked to be the bad guy.
• Work with my wife to understand more of the 'why' MIL feels like this is so important. We’re both still adamant that we do not want folks we’ve never met tagging along, but maybe we can help MIL to feel better about things by tackling other issues.