I’m sorry to hear that your mother-in-law is reaching her final stages of life 
@starborn provided a beautiful ritual (it’s gorgeous!) and I don’t personally have one to add. There is a book by Mortellus titled Do I Have To Wear Black? that I own (but haven’t gotten a chance to read) that’s all about pagan funeral rites and customs. Your local library may have a copy, or there may be a copy on Scribd.
→ Do I Have to Wear Black?: Rituals, Customs & Funerary Etiquette for Modern Pagans by Mortellus
We also have a few spells on the site and forum, too. I’ll grab some links! I also agree with Starborn that the poem you have written is perfect for your ritual, too. Bringing personal words into the ritual is a wonderful way to make that connection
→ Wiccan Prayer for Death of a Loved One / Loss of a Pet – Spells8