Sudden change of behaviour

I would be great for any help and advice!!! We have a Female German Shepherd Rescue dogs who is around 4 years old (Kiki)and has been with us for about a year now. Having lost our German Shepherd Boy dog who was 13 Years old in January we took on a 6 months old German Shepherd Rescue dog(Monty) to keep Kiki and us company! Kiki was a loving and great Mummy to Monty when we brought him home and was this way untill 2 to 3 wks ago just before our move to a new house! She then started pinning him down for what appears to be no reason like out on walks (on lead) she has suddenly jumped him and yesterday we were hanging mirrors and Monty was interested in the measuring tape she lept on him then she is definatly hurting him emotionally and he does yelp and wee ! we put her in the garden or garage for five mins or if its outside I put her back in the car so she forgoes her walk !
   
We have just moved home from an apartment to a largish house (comparision ) and we have a garden again ! the problems started when we were packing we thought it was because of the unsettled enviorment !? and that it wld pass !
   
Kiki came from a gsd rescue in U K and was with our older gsd who passed in Jan this year (she was My new little girl as we had our previous girl pass the previous Jan ) We new she had in our experiance been v good with all dogs and is nearly perfect in everything and has obviously been well trained b4 which is why her bahaviour is so shocking !!!!
   
She is very much totally focused on me always has been ! and I pay close attention to giving her attention rather than overindulging the pup altho now she and he have to "work" for attention and treats as in come when called sit down etc !!hope you can help !!! Im at my wits end as even tho having shepherds for over 20 yrs and combined ages ! and used to have my own animal care company for years in uk (home visits and walks gen care ) im at a loss ! Thanx in advance for your help!!!