I rehomed a 1 year old collie yesterday. I am determined to do right by her and have booked into one-to-one puppy and agility training as I'm new to dog ownership. So far she has been a dream in most ways. She is very affectionate but didn't disturb me at all in the night, had free rein of one room while I went out for an hour and didn't mess or destroy anything. She loves fetch in the garden and frisbee in the local park and her recall seems great, though I haven't tested her off lead outside of the home and garden. With a long training lead in the park, her recall was fine.
The only real issue I am having is walking her on the leash. She came from a multi dog household where they didn't really walk them per se but drove them to a big field to run about twice a day and gave them free run of the garden. I was told she sometimes barks at other dogs on leash but is fine off lead.
My experience is that she is terrified of other dogs, growls at them and if they are close, lunges. When an off leash dog came up to say hello at the park, she lowered her body and showed her teeth and he trotted off.
Is this just insecurity at her new home, or do I need to train her out of it and if so, how? Thanks in advance!