Cassandra/Angelique must be in seventh heaven running into all these folks who looked like the people she had known in 1795.
It was only natural that she chose Maggie (the spitting image of Josette) as the first one to have the dream....still it was rather mean of Cassandra to make her have the dream almost immediately after Maggie was so friendly to her. But then most witches aren't known for being nice, are they?
As for Maggie taking in Jeff, well at this point, Sam is still around at this point (though we don't see him as often as we use to) I suspect they did it as a favor to Vicki, they are close friends of hers. If Vicki insists that Jeff is trustworthy, no bother to anyone, nicest guy on the planet, etc. etc., then they must have trusted her judgment.