I'd go with the 1st one.

The second one is not a professional nanny and will leave when she finds something better.

#1 not only has nanny experience (5 and 7 are similar enough), she’s raised her own kids. References speak to her ability to speak the language and help with academics. If she didn’t have at least passable English, I’d suggest bypassing her.

#2 has no experience with children, either paid or otherwise. Nobody counts helping with siblings towards experience, because there’s no way to really know how many hours it was or what was expected. She’s also not interested in childcare as a career, which leads me to think that she may not be the right type to keep a child focused this fall/winter.

If you think #1 can handle the academics, she’s a shoe-in. If you don’t think she can handle it, pick #2.

I concur that a young Nanny is more apt to be on her phone more.

Just make sure to stress very well that her phone usage should be minimal.
And make sure to be proactive that she adheres to your request.

Good luck in whatever you decide!