I am very surprised to read that mom stated she wouldn't do anything differently.
For me, any judgements in missing childrens cases are often based not just on the fact that the parent wasn't watching their child at that moment, because 99% of parents have some sort of story to share where they lost sight of their child, (in fact, almost every case, posters here will share their own stories) but the how and why are what I tend to focus on. To me, what the parent was doing instead plays an enormous role in my overall feelings about it.
Imo, there's a difference between turning to grab some cereal off the shelf while grocery shopping for your family, scratching it off your list then looking back up to find that your child is gone/has run off/run ahead an aisle over/has hidden behind bulky items in a lower shelf. (A narrative often shared here)
and
Going to the park, staying in the car despite the children not being in view scratching off lotto tickets instead and having an 8-9 year old have to bring your attention to the fact that the kids haven't been seen for the last 10 minutes.
Playgrounds aren't as safe as people assume, and not because there's dangerous people lurking around waiting to steal your children. Injuries are the #1 issue. Accidents happen and you sometimes can't prevent them, but having your eye on your child(ren) definitely helps in terms of coming to their aid fast should an injury occur.
CDC - Playground Injuries
Not to mention, sometimes kids can be jerks at playgrounds. You want to be sure you're within an earshot and can see what is going on because sometimes kids don't know how to play nice with others and you don't want your own child being treated poorly or worse yet, your kid being rude to others. Hard to gauge the situation if you can't hear and aren't watching.
I'm just rambling on at this point. Kids get lost, parents take their eyes off their children, It happens. It's avoidable, but it still happens. We tend to polish our parenting skills from our own past mistakes & oversights or those of other parents. To simply say there is no mistake, there is no oversight, it was completely unavoidable, or that you wouldn't change anything about the situation, while it may spare a parent of feelings of guilt or embarrassment, it doesn't teach anyone anything in what I think are very important, teachable moments.
All the main safety precautions I take are not because I was born with the gift of being a knowledgeable person but because I've learned from other people's bad experiences or mistakes. To answer that no, there's nothing she would have done differently about the situation is surprising and a bit alarming to me, especially considering there is a still a 3 year old and a new baby on the way. I can think of 2 things I wish I'd done very differently just yesterday and none of those situations ended in tragedy by any means, but when thinking about them afterwards, making some changes would have given me better results. There's always something to be learned, there's always a teachable moment.
I hope little Dulce can be found safe and returned to her family. My years here have made me jaded/pessimistic in terms of that happening but I still wish for that so much for Dulce and her family!