'Puppy' redirecting onto older dog

Need some help :(

My 10month old 'puppy' (Nixie) is redirecting her frustration onto my 6yr old male, Seven.

Tonight on our walk, a gentleman with a dobe stopped to talk to us & wanted to see my guys. I don't like strange dogs coming up to my guys while they are on leash, so I was politely removing ourselves -- all the while Nixie was barking & carrying on. Maybe 15 sec into this, Nixie redirected onto Seven (launched onto his back & started to bite him). I removed her and promptly placed her into a sit -- she willingly followed but did not stop barking.

I find that around the house she is constantly slamming into him, and directing his movements. I body block her away, then make her down or sit & give me full focus, before releasing our interaction.

I'm looking for solutions and training advice. I'm thinking I need to start using a Gentle Leader on our walks to refocus her and help set up the opportunity to reward her good choices. If this is correct, could you please advise me on how to use it for our situation? (turning pressure on & off etc)

Asides from dealing with her reactivity to other dogs when it is happening, are there things I can work on around the house to enforce that these things will not be tolerated? Saint Seven is not a punching bag!