I think DM might have said to LE when they asked her about her "state of mind" in the hours between seeing the masked man around 4 am and the call to LE after 11 am, that she was or must have been in a state of "frozen shock" and they "tagged on" the word "phase" because it implies she may have gone through several different phases or stages/states of mind throughout that morning.
For example:
An earlier phase could have been that she was groggy and upset at having been woken up by loud noises that she thought were from her housemates being rambunctious or "partying and horsing around" super late -- the "things are out of hand with my housemates phase".
Then after she had yelled out at them that she was trying to sleep and opened and closed the door 2 times, there was another phase after she was startled enough by seeing the masked man (unknown person who could have been a late night guest) in the house the 3rd time she opened the door to then close and lock her door, but was still assuming the noises had been from horsing around and he was just a guest "leaving" as he passed by going in the direction of the patio doors -- the "things finally quieted down but I wonder who that was" phase.
Then there was a phase where she thought more about the masked man and whether he made sense as a late night guest (wearing a mask due to Covid or other illness? wearing all black because some people do?) trying to process what seeing him "going towards the door" around the same time the house became quiet meant, then trying to reach out to her housemates on her phone to check in, and them not answering with her maybe thinking they broke up the party and sent guests home and finally are really trying to make sure everyone is super quiet and going to sleep" -- the "they must have finally kicked everyone out and now they've crashed out" phase.
Then there was a phase where she maybe considered other scenarios, especially if the masked man seemed "off'" for a typical late night guest and her housemates not answering made her increasingly uneasy (were they all 'locked down' staying silent in their rooms after sending a troublemaker on their way and promising not to call the cops on him?), such as someone showing up who had been to a party there before who was inebriated and wanted to crash there uninvited and ended up getting in a fight and making someone cry, or some random creep showing up and causing trouble or trying to sexually harass or assault one of them, and the noises she heard were them dealing with him and he was "sent on his way" and they all went back to bed after comforting whoever she thought she heard crying and locking their doors -- the "but what if that was a 'bad dude' in the house, one of them would have told me, right? phase".
Then there was the phase, perhaps intermixed with sleep and checking her phone for any delayed responses from housemates or friends or anything on SM from them, where she was dwelling on the more sinister possibilities but not being able to confirm anything, wondering if she misunderstood what was going on, sitting alone in the dark and getting more and more petrified of the "bad dude" who could still be in the house or lingering watching the house to make sure no one 'called the cops', thinking of other reasons why he could have been there, what he may have tried to do or done, or could still do to her, but being in disbelief or denial of anything really bad happening without her knowledge or one of the 5 other people in the house raising the alarm -- the "frozen shock phase".
JMO