Mira informed Maria and Celaine that she planned on not leaving her room until she broke through to the Peak of the Foundation Realm. They both understood her and decided to focus on doing their own things. For example, Maria can still try and learn more about alchemy while Celaine… Well, she was just going to consolidate her gains during her time in the Secret Realm. Her saber skills have advanced rapidly over the last 3 years and she's barely had any time to meditate on them so she might as well do it now.
As for the matter of leaving the Sect and making it in time to advance to the Core Formation Realm and take part in the Entrance Exam of the Main Sect? The three of them aren't worried about this in the slightest. Having Elenei with them can literally save them months of travel, even if they are going to separate. So it'll actually be quicker for Maria and Celaine if they just wait for Mira to finish her business before they leave.
