tbh haven't seen the manga beyond the 1st 6 translated chapters but from what I have seen so far think the tv series is running its own version of mai otome different from the manga just like they did for mai hime. So therefore drawing comparsions between the two are rather pointless.
For those who have seen eps 17, do you remeber smith saying that arika's robe wasn't fully powered up, I thought he just meant that she hadn't used her crystal staff/weapon, but recently I got thinking, if you compare all the other full active robe's like ultimate black diamond/amythest/silver ice/topaz ones they all look like a set of robes in design, but arika's just looks like a different coloured version of the coral/pearls ones, which makes me think her robe will either change into an new unseen version or like the one the previous user was using (the one you see the new opening)
As for todays eps, have to comment to all those people who said on last poll that arika went back to her grandmothers are likely to be very wrong after all the reason she left was because she was dead therefore the lady you saw in eps 18 can't be her grandmother.
As for my predictions
On a final note have to wonder if we are ever going to see some serious fighting in this series or not? with only 8eps left including this one isn't much time left to get some action on screen. Most of the fight scenes we have seen are very short or we only get to see parts of the fights.