Hollie, who is originally from Pwllheli but now lives with her husband and daughter in Wrexham, received her diagnosis last October.
She said she decided to write the book to try to explain to her daughter why she spends more and more time in bed due to her illness.
Hollie, a teacher at St David's High School in Saltney, wrote most of the book in bed, one sentence at a time, in periods when she was not sick from the chemotherapy. After four months and several changes, the book was ready for printing.
Hollie said: "When they gave me the diagnosis eight months ago, the first thing I thought about was what I was going to tell my daughter, Sydney, who was only three at the time.
“At first I tried to keep it from her, but children are not stupid and she soon knew something was wrong because I had gone from being a very energetic mother who did things with her to just lying in bed, very ill."
Hollie received six rounds of chemotherapy, and noticed at the time that there was really no literature available for children on this issue, which affects thousands of families in Wales every year.
The book is now available in Welsh, ‘Weithiau, mae mam yn teimlo...’, and English, ‘Sometimes, mummy feels...’ in local bookshops, or online, with all proceeds from the sale of the book going to cancer charity Macmillan.