I would follow some introduction instructions. this and other website have them.
It's not a race.
give them plenty of time with scent swapping.
you might want her to grow a few months before introductions.
after awhile you could try a one to one in tub see how it goes before
putting all 4 together.
Even after scent training introductions can be easy or difficult. you should
have one alpha in the group that might not want her, so they could just spat once
or twice then be ok, or ball up and need separation, so ALWAYS have a fleece
cloth around so you can use your covered hand to separate them, and reduce getting