I agree that it is still early days!
Additional “pre-bonding” time could help. So in addition to side-by-side living, start swapping who is on what side every day or two, and continue that for a couple weeks.
Growling and lunging are actually OK, as long as they don’t actually fight. it’s all part of them communicating and setting their boundaries with each other. She may growl if he moves too close to her too quickly, so that’s her telling him to slow it down.
I would keep going as you have been, and try to always end the session on a positive note. I like to do a lot of petting as well during early bonding sessions, so when they approach each other don’t be afraid to pet them.
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The answers provided in this discussion are for general guideline purposes only. The information is not intended to diagnose or treat your pet. Seek the advice of your veterinarian or a qualified behaviorist.