The two-year-old is battling against two forms of leukaemia.
It was reported last month that Margot was living the rest of her life at home after specialist treatment was unsuccessful.
Parents Yaser and Vicki, originally from Essington, said the youngster underwent chemotherapy last Friday in an attempt to reduce her white cell count.
However the treatment had little success, and since it was stopped Margot has been feeling better.
She has also been due to visit Great Ormond Street Hospital in a bid to manage her symptoms, but took a turn for the worse and was taken to Kingston Hospital instead.
Margot was diagnosed with both acute lymphoblastic leukaemia (ALL) and acute myeloid leukaemia (AML) last year.
Her fight against the disease has captured the hearts of people across the country, with 17,000 people now getting updates on the Team Margot Facebook page.
The latest post from her parents said: "Generally Margot has been clinically well over the last few weeks, although she had a rough weekend after starting a course of chemotherapy on Friday.
"This was an attempt to try and reign back her rapidly rising white cell count; however, it made her unwell and only had limited (if any) success.
"Since we stopped administering the chemotherapy Margot has been feeling better although she is increasingly more sleepy as the disease progresses.
"The plan for today was for us to visit Great Ormond Street Hospital for a lumbar puncture procedure.
"This is all part of the symptom management process and the aim is to inject chemotherapy into her spinal fluid; we don't want any leukaemia getting into Margot's central nervous system - there is a tendency for this to happen as white cell counts rise above 50.
"If this were to occur, symptom management would become far more challenging.
"As of yesterday, Margot's white cell count was recorded at 53.6.
"Unfortunately, Margot's temperature spiked & she vomited during the early hours of this morning, so the lumbar procedure needs to be rescheduled and we currently find ourselves at Kingston Hospital instead."
Margot, who has two brothers Oscar and Rufus, was diagnosed with an extremely rare form of leukaemia last October.
A Swab4Margot campaign, backed by celebrities such as Stephen Fry and John Bishop, led to more than 50,000 people requesting swab kits from charity Delete Blood Cancer UK.
Eventually a match was discovered and the operation was deemed a success, however tests in June showed traces of the disease had returned.
Her parents said these were 'extremely difficult times' for the youngster.
They added: "We are working with the palliative care team to try and manage her pain to ensure that she is as comfortable as possible and infection free (she is severely immune suppressed).
"These are extremely difficult times for Margot and the rest of our family and we are so grateful for your continued support and well wishes."