Okay so you've asked for it straight. I'm sorry to be so rude but:
Grandparents who have to care for their grandchildren have been put into that situation.
Your child would have the double whammy of you being unusually elderly - but also of you being unusually selfish and frankly, weird enough to have gone ahead with solo IVF in your mid-50s.
No dad. No grandparents. No brothers or sisters. No aunts, uncles or cousins. Just them and one very unusual old lady.
My parents are currently in their early 70s having had me in their mid-30s - I love them but they have changed as they aged. Their faults are magnified. They are a little slower, frailer, more needy, more anxious, more set in their ways, weirder, more resistant to change, and far less adventurous. I know that not all elderly people experience these changes (my Dad has held up far better than my Mum) but many do. My parents are doing fine because they're at a stage in their life where they don't have incredibly demanding responsibilities. I'd like more of their support but I don't need it because I'm a grown woman in my 30s with my own family.
I cannot imagine being 20 years younger than I am now - being only a teenager - and having only my mother as she is now. To be honest, it would have completely f*cked me up.
The ship sailed at least 10 years ago. You still have time to lead a good, fulfilling life but not to bring a child into the world and raise them from birth.