Grandparent disappointment

How do you deal with disappointment in a parent that isn’t as helpful or present in your kids’ life as you hoped? I didn’t realize that I had expectations of my mom as a grandparent until I was completely blindsided during the pandemic by her unwillingness to be there for us/my kids when the world shut down. Fast forward 5 years (and 3 kids), and my frustration has peaked. She says she wants to be the first call if our nanny can’t come in, but when she is watching my kids she ALWAYS comments on how hard it is. I get it, three kids are ALOT, but it really freaking bothers me that she is so vocal about how difficult it is to be here with my kids who mean everything to me. This weighs heavily on my mind as someone who struggles to ask for help (my husband and I have been on ONE date in 6 months and if my nanny needs a day off I just take a day off too). When you contrast it with how often she takes care of my niece, an only child who spends the entire weekend there at least twice a month, I feel resentful and sad.

Most of my frustration stems from the fact that everything has to be on her terms. During the pandemic she was willing to help but didn’t want to be nailed down to a specific time (daycares were closed and I just needed to know when I could plan my focused work time). Today she’s covering for my nanny who is on vacation and she was late, and also TOLD ME to watch my daughter while she took my son to pick up my other son from school. It’s like she has to assert dominance or something, and if we can’t accept that then we’re ungrateful for her help. My brother turns a blind eye to her accusations of being ungrateful and just takes the wrath in exchange for free childcare but I can’t separate my feelings which is why I rarely ask for help.

I recognize that this is Reddit and this lacks a lot of nuance / context but I just feel bummed and not sure how to move on from here. Any advice?