If it makes you feel any better, the reason why this one is less insane is because pre-reboot, Red Arcueid is a TATARI version made by Wallachia, made in the way of what would happen if Arcueid succumbed completely to her loss of control. Since Wallachia is not here, this is the real one, and the real one can control her powers. Kind of reminds me of Fate EXTRA, where she appeared as an enemy servant (that was so awesome... was also so hard) and she only wound up insane due to being summoned as a Berserker and her Master's delusions about her that warped her that way, otherwise she would have been fine.
YOOOOOOO WTF Pretty sure everyone expected either Aoko or Mario to come but certainly NOT this Arcueid. Looking at the Remake again (oh and fighting against Ciel), yeah this is definitely a HUGE spoiler lmao
To be fair, she generally appeared that way in the Melty Blood cutscenes- the same as normal Arcueid, just a bit more psychopathic. It was only in certain moments that she looked utterly unhinged, so I wouldn't worry just from a short snippet.
