I don't think Gizelle is neglectful. I actually thought that was ... I'm not sure how to phrase this, but a way of illustrating what a family friend told me when I was about 21-22: you can have it all but you can't have it all at the same time. Gizelle is a single (and if I recall correctly, her ex-husband lives in another state so I doubt she's handing off the kids every weekend) mom of three who has a business. She's busy. She said herself that she felt like she thought her kids were seeing her as a strong woman building a business for them, but she didn't know her kids felt like she was falling down on the mom job. If you're a working parent, odds are great that you're going to miss some soccer games.
Her kids do seem bonded to her and comfortable enough with her to tell her how they feel - it was probably hard for the twin who feels neglected (I don't know which twin is which - I know Grace is the oldest and the other two are Angel and Adore, but I can't tell the twins apart) to tell Gizelle that but she did, and I think Gizelle heard her. I don't think Gizelle is neglectful in, like, a CPS sense; I just think she's busy juggling and sometimes balls get dropped. I thought it was a rare moment of vulnerability for her.
Re: Gizelle being introverted, she may be. She seems to like her alone time. I am an introvert, and when I tell people that they are always shocked. I recharge by being alone. Extroverts recharge by being around people. I think there's a misconception that introverts are shy and socially awkward, when introversion, shyness, and social awkwardness are three different things - you CAN have some combination of them, but it's not a guarantee. I highly recommend the book "Quiet: The Power of Introverts in a World that Can't Stop Talking" by Susan Cain - it helped me understand MYSELF better, because it breaks down all the different kinds of introversion (and there are different kinds!)