
The blanking is your bitch showing the other she is boss, and only when she feels she has made her point sufficiently and the other accepts it will she unbend and maybe make friends. By shutting the ther away you aren't giving them the opportunity.
Do you never have other peoples dogs to visit in your home? If you do and your bitch is civil then act the same with these two.
If your girls is not used to canine interlopers on her patch then you will have to introduce them together in areas least likely to cause conflict (feeding and resting areas) and stand back ready to intervene if anything serious kicks off, but leave them to it.
Personally if the young one is unreasonably aggro to the other even if the other minds her own business and accepts her Alpha position then I would have words with her to make it clear she is to be well mannered, but otherwise let them find their own level.