NO. REHOME YOUR DOG. What a mess. Yes of course you need a muzzle now.
Sorry but you don't have enough experience or the right leadership/disposition for your dog and LOVE is probably why she's that way. Even though you THINK you do. YOu need the rehab before the dog can be rehab'd.
ALL THE SIGNS WERE THERE and you ignored them - sorry not a read or criticism just the truth. I'm positive you missed PLENTY of other dog signals. Sometimes it's only a GLANCE. Head placement. Tail placement.
Do what's best for HER finding her an appropriate experienced home.
With all your "handler" experience/connections and her experience it should be quite easy to do.
Didn't you know that a female GSD is the quickest most accurate biter on the planet? Just for starters.
Thank you for PROVING all the "training" in the WORLD does NOT make up for being a true LEADER with a BALANCED PACK and that some dogs just are NOT suited to living in some homes with certain type of "leadership" (or lack of), especially when baby's lives are at stake.
A GSD is ALWAYS waiting to get your car keys and check book when her "time" comes.
All the trendy mumbo jumbo terminology.Resource guarding...leash reactivity....on leash ~work.... Gurl ,leash reactivity comes from THE HANDLER. Yes I realize you said she stopped that but you did NOT say that she can be safely walked in the company of dogs etc. So there's some info missing here. Of COURSE she's seeing the baby as a dog. She was not told other wise that the baby is HIGHER in pack ranking. (And I doubt it would matter to her anyway at this point).
SHE'S STILL NOT GOOD WITH OTHER DOGS.
The KEY GOALS are: LEADERSHIP. BALANCE. RESPECT. EXERCISE. DISCIPLINE (self discipline) and YES: SUBMISSION. NOT FEAR SUBMISSION - RESPECT submission of waiting to be INVITED to "participate".
You don't have that. WHY would you be giving her access to SHARING YOUR FOOD with HER HISTORY? More evidence that nobody who understands dogs really helped you with her. Or you did your own thing. Food is affection. Food is power. Food is EARNED. It's all body language and leadership and energy not "training" or "commands". Although sure sometimes "commands" can convey leadership but they are NEVER necessary with good energy and leadership. Sure commands can train stuff like retrieving or even a verbal command can be shorthand but a look or a gesture or posture gets you a better response if you are a LEADER and respected as someone who they can TRUST in the world.
Your dog should have understood that that BABY is in a higher position than her in the pack and of course because you never SUCCESSFULLY REHABILITATED her ongoing ISSUES that was not possible. You were "MANAGING" her not REHABILITATING her brain. Yes I understand you tried your best with what you thought you knew.
And OF COURSE that "sort of violence" that is still obvious three hours later is the worst possible thing you could have done. She is also mirroring your instability.
In your dog's eyes she had a simple dog disagreement over YOU.
Just like she would have done with another dog (wrongly). She needed to be brought back INTO the pack not isolated. You broke the trust bond if it was there to begin with.
LOVING YOUR BABY is NOT A GOAL.
Only a LEADER gets "RESPECT" in a dog pack even a baby who STILL needs to be PROTECTED AT ALL TIMES with ANY DOG.....and this is a LONG LONG LONG slog that is questionable at BEST and a disaster for your dog ending up likely being euth'd. Obviously the baby is at the most risk too god only knows how you were lucky she didn't lose an eye get gashed in the face etc.
Because of MOM, sorry.
I'm not trying to make you feel WORSE but I am trying to make you realize what's going ON HERE.
BTW I'd get her a FULL PANEL THYROID test PRONTO. Just a hunch. It's not cheap and it may not show anything but still....This dog has obviously shown the ability to LEARN from what you said so if she's not thyroid it's YOU. Well, it's you even if she's thyroid LOL. No offense really, just trying to make you see she is NOT hopeless in the right hands.