Mystery behind the secret door

MUM

When Agatha was through with whatever she was doing, she entered her room to rest and 
She had a dream that goes like this
   "Agatha my child, I've missed you a lot"mum said
"I miss you too mum, you won't go again, will you?"Agatha asked curiously
 "You know what?"mum asked
"What?"I inquired
"Tell me about your day(s)"
"It was kind of tough,many people bullied me, especially those my naughty, foolish class mates"
"You should have Beat the Hell out of them "mum said
  "I wanted to but I don't want them to cry "I replied
"Or you can't beat them "mum said teasing me
   "Mum, like seriously, I pity them"I said trying to defend myself
    "Why?"Mom asked and I ran out of excuses
    "Emmmm be...... because.."I stammered not knowing what to say again
    "What about Alexander?"my mom asked and tears rolled down my eyes
     " She is gone"I replied
"To where?"she asked
    "I don't know mum but I can't find her, I searched for her for years but didn't see her"I said crying
    "Alexander has always been with you and don't forget 'THEY WOULD BE COMING FOR YOU"my mom said and starts to fade
   "Who would be coming for me Mom "I said trying to get hold of her but I couldn't
     "Mom!!!!!!,Mom!!!!!!!!!!!"I screamed many times and woke up immediately
    "Am always here for you "I heard Alexander's voice
     "Alexander "I said kinda shocked and at the same time checking to know where the voice was coming from but I didn't see her but the only thing that I kept on repeating was that 'THEY ARE COMING FOR ME!!!!!!!!!!!!!!!!' and that made me kinda crazy and confused at once