It seems uncharacteristic of Cassandra to be so friendly to Julia. It must be that she sees Julia as a serious threat. I suppose that when Cassandra learned how Julia had aided Barnabas in saving Dr. Lang from Roger, she decided that Julia was a problem. Cassandra may now be hoping to distract Julia by getting her romantically interested in Professor Stokes, or she may just figure she'll be able to keep better track of Julia if she and Julia are friends. I'm not sure, though, why she didn't do the easy thing and put Julia under a spell. Two possibilities occur to me: first, she tried and failed, due to Julia's genetic structure, which is mentioned later on in the series as being something out of the ordinary. Or else, being Cassandra and not Angelique, she is not interested in simple solutions, and figures that she'll be able to inflict more pain by using non-spell-related methods.
In any case, Julia is having some fun of her own with Cassandra. Saying that she admires honesty in people! For all I know, she does, but she's never bothered to cultivate honesty in herself.
Jeff was astoundingly easy to hypnotize. Weird.