LesLu13
Got a little confused there with the cage plans, lol.
What I meant, was:
1) Place new Finch in quarantine, in a cage away from your other birds; another room would be preferable. Some people recommend a full 90 days of quarantine, others claim 2 or 3 weeks to be sufficient.
2) Once the quarantine period is over, place new Finchie in a cage next to Lulu, so that they can get acquainted, without being actually placed together. This can be from a couple of days to a week, or until you notice that they're interested in each other (in a good way, not charging and hissing at one another).
3) At this point, I would take Lulu out of the finch cage and rearrange it .
4) Once this is done, I would introduce both girls into the newly decorated cage together.
I know it sounds confusing, but in the long run, it seems to (usually) make the introduction and transition easier, and tends to cut down on aggression between two stranger birds.
Regretably there is no sure way, or fullproof way to guaranee that they will love each other, and never argue or fight. However Zebras being very social birds, will usually gravitate towards the other bird, and eventually form a bond.
All we can do is hope for the best
.