Daisy is crazy

This theory is a bit far-fetched, but has been proposed by several people in the comment sections of the videos and is one of the more interesting theories. The general basis of this theory is that Daisy clearly suffers from one or more mental illnesses. Most videos include her dealing with anxiety as she speaks with low confidence, gets choked up about certain things, and is afraid to go outdoors and interact with others.

It is possible that she is suffering from anxiety, or she may have a delusional disorder, and/or a dependent personality disorder.

DSM-V Definitions of Each Disorder and How They May Affect Daisy
Generalized anxiety disorder (or GAD) Delusional Disorder Dependent Personality Disorder
 * restlessness or feeling on edge - Daisy is constantly seen tapping her fingers or shaking her leg in videos, even when there does not seem to be a reason. She is also almost always on the brink of tears. 
 * irritable - as we get to know Daisy more, she seems to have breakdowns more often, indicating her irritability increases.
 * trouble focusing and concentrating - She has a hard time getting her words out in fluent sentences. She says "um" a lot, especially in the first videos. 
 * insomnia - She blames Alan for not being able to get rest, and tends to stay up all night and sleep all day due to the day being "dangerous"
 * Distress or impairment in social, occupational, and other important areas - Daisy has no friends and does not go outside to interact with others. She only occasionally talks to people online.
 * Although these criteria seem to fit Daisy perfectly, she cannot be diagnosed with GAD if there is another underlying disorder including a delusional disorder or schizophrenia. This does not prevent Daisy from having GAD, but it does not prevent Daisy from having paranoid schizophrenia or delusional disorder.
 * Having GAD does not create delusions and hallucinations, so perhaps Daisy knows that Alan is not physically there, but he acts as a stand-in for the audience to prove that anxiety is a real problem and a real fight. At the beginning she is tending to him, and trying to take care of him to the best of her abilities, but since she is alone without any help from her father, she is struggling to control the beast. Without help, the anxiety grows stronger and stronger until she begins to have mental breakdowns. Without the social support and professional help that is needed, anxiety, just like any mental illness, can worsen and begin to take over a person's life in debilitating ways.
 * At least one delusion -  It is likely she has persecutory delusional disorder, and she believes that she is being mistreated or targeted by the "dangerous" people that her father had told her so much about. This is why she refuses to step outside during the day, because she has so ingrained the fear that people will try to hurt her. 
 * Hallucinations - Daisy may be having hallucinations of Alan, when in reality, he may not actually exist outside her mind. She may have created Alan as a coping mechanism for her father emotionally abusing her, and then her hallucination turns on her and begins to abuse her too due to the traumatic and familiarity of her father's abuse. The scratches and blood on her body could be a result of her own self-harming or tendencies to pick at her skin.
 * difficulty making decisions, needs a lot of advice or reassurance - Daisy constantly talks about finding the notes to be sure that she is taking care of Alan to her best ability. She also asks the viewers if they think her plants are healthy or if she should do something differently. In some hidden captions, it is plain to see that she has a low self-esteem and is seeking approval from viewers and is trying to impress them to get them to like her.
 * trouble disagreeing with others in fear of abandonment - When her father would shut her down for asking a lot of questions or told her to go out and try to find the good people on her own, Daisy quickly retreated into her shell and would cling on to her father in fear that he would leave her. 
 * trouble starting projects - This does not seem to be a big issue for Daisy, as she seems to be able to initiate her own projects.
 * excessive lengths to please others - She was always very obedient to her father in order to keep him from getting angry with her. She tries to recreate beauty guru channel videos in order to attract a larger audience online. No matter how much abuse that Alan puts her through, she still sticks with him and does not try to harm him like he harms her. She desperately wants Alan to like her and be grateful for all that she has done for him. 
 * fear of separation or abandonment - Daisy has been abandoned by her father and she does not know why and may blame herself. She is secretly afraid that Alan will abandon her and she will be completely alone. 

Other Interesting Facts That Indicate She is Mentally Ill

 * At the beginning, Daisy feeds Alan sugar pills, which may represent Daisy taking her medications everyday. Once she switched Alan over to sugar water, things slowly started to get out of Daisy's control. Alan started to grow and become meaner and meaner. This could be the voices in Daisy's head telling her that she is stupid and worthless, and that no one will ever love her. Now that Alan is way beyond eating just sugar pills, it may be too late to save Daisy.