As for ladies watches and durability... I'd nix Piaget. They make great watches (I was looking at several of their watches the other day). I love their dress watches but I wouldn't choose one as a daily wearer especially if it might get exposure to water.
Cartier makes some great watches, the Santos, Tank Francaise, and Pasha. If 100m of water resistance is crucial to your mom, it might limit some of your choices. I think the Santos & TF are only water resistant to 30 m. I can say my wife has had a Tank Francaise as an every day watch for 10 years & she loves it. Never had a problem with it. It's gotten wet, but she hasn't taken it swimming. She has the large steel automatic which isn't that large by today's standards.
The Rolex Datejust isn't that unusual, but it's incredibly versatile, durable, and it's water resistant to 100m. Your mom would also have a choice of several sizes and all steel or steel & yg or steel & rose gold. My wife has one in steel & rose and she feels between the TF and DJ, she has some very versatile watches that cover her needs. Whenever she starts look at true dress watches she gets distracted and ends up choosing jewelry instead of a watch.
Chopard, makes nice jewelry, but I've never met anyone that owned one of their watches, so I can't say how durable they are.
As for Omega, my wife thinks the Speedy Pro is good for a man, but she doesn't like their ladies watches at all.
The best thing to do is to take your mom shopping and see what she likes.