Narcissistic mother

'll try to keep this as short as possible.

I'm a grown woman with two children, and it wasn't until I became a mother myself that I realized my own mother is a narcissistic manipulator.
I moved 400 km away for university, stayed there, and built my own life with my partner.
Ever since I had my first child, my mother has become emotionally dependent on my kids. She admitted she was diagnosed with depression and has openly said that spending time with her grandchildren is what "heals" her. She's even made comments like, \*"I'm glad your in-laws don't visit very often because that gives me more opportunities to come."\*
After my first child was born, my parents visited about once a month because my mother regularly traveled to my city for work. Now that I have a second child, she says things like, \*"We barely know him because I don't come here for work as often anymore."\* My baby is five months old, and they've seen him exactly five times.
A few days before arriving, they'd simply text: \*"I'm coming for work, so we'll stay at your place from Thursday."\* They never ask if it works for us. They always come together—my mother and father—and just assume they'll be staying with us.
They act as though they have more rights to my children than my husband's parents do.
Growing up, my younger brother and I constantly walked on eggshells because every day depended on our mother's mood. She had a difficult upbringing, so we tried to be perfect children to avoid causing her any additional stress. Looking back, everything revolved around her. She monopolized every conversation, always had to be right, has no hobbies, no close friends, believes everyone is against her, and constantly gossips about other people.
Since my second child was born, I've started setting some boundaries. Her response has been coldness and emotional distance. We barely speak now—maybe once or twice a week. When she talks to my older child, she asks things like, \*"Do you want to come to Grandma's?"\* or \*"Do you want to go to the beach with Grandma?"\* It feels like she's trying to paint me as the mean mother who won't let her child see their grandmother.
Every visit feels emotionally draining. She sulks, stares into space, creates a heavy atmosphere, and only talks about negative things. She even chooses travel destinations that conveniently pass through my city so she can stop by or stay overnight without asking if it's okay.
The hardest part isn't saying "no." It's dealing with the guilt afterwards.
I have a very supportive husband who keeps telling me to ignore her behavior, but I can't. Just thinking about her gives me a knot in my stomach.
My dad is a reasonable man, but I think after spending his entire life with her, he's simply exhausted and has learned that it's easier to give in than to challenge her.

\*\*How do you set firm boundaries with a parent like this without feeling overwhelmed by guilt? Has anyone else dealt with something similar?\*\*