What your older dog does is textbook parenting. She took over the responsibility of teaching the puppy how to act and what not to do, of course in dog language.
Dogs cannot scold their children with words, revoke TV privileges or put them on house arrest. They use their snouts to reprimand each other. The fact that the puppy didn't yelp or whine means that the older one was gentle in her reprimand.
The bowing and pouncing sounds like the "play bow", an invitation to play in dog language. You should only interrupt her if she's too rough with the puppy. Please have a look at this very instructional video, that explains dog body language in situations like anxiety, aggression and play.
Now the situations you'll want to intervene in:
The older dog snatching up the toy is plain jealousy. She doesn't want to share her toys with the puppy and tries to put them out of the reach of the puppy. This is only acceptable to a small extend. As Allerleirauh wrote in their comment, you could designate some toys the "property" of the older dog, but most toys should be shared by both. Otherwise this jealousy could transform into excessive guarding and aggression soon.
To make it clear, that toys are to be shared, either play with both of them at the same time with the same toy (let both of them have the toy equal amounts of time), or take the toy away if the older wants to hoard it. If they play with each other, let them have the toy. Only take it away if the older one tries to hoard it.
If the puppy already had the toy before it was snatched away, give it back to the puppy and keep the older dog from taking it again. If the puppy didn't have the toy, put it back on the ground and keep your older dog from taking it again for a little while. If the older dog won't give up, take the toy away entirely for a while (like an hour).
And lastly the fixating and following the puppy. You must understand that your older dog took over the job of "nanny" or "teacher" on her own. This happens often if the dog doesn't see anyone else fulfilling the particular job. Someone has to do it, so before no one does it, the dog takes over. You must also understand that taking such a job for a few hours a day is ok, but taking it as a full-time job is very stressful for your dog.
To discourage this behavior, you have to show your older dog that you take over from now on. You have to train your basic command like "sit" and "no"puppy and (gently) reprimand her for bad behavior. You also have to discourage your older dog from following the puppy from time to time. Just call her name, gently pull her aside and engage her in any activity like training, play or cuddling instead.
