The issue is not neccessarily because she'd be a single parent with donated sperm, it's the sperm is coming from a dead man that she used to love and is probably using the sperm to mask the fact that she can't get over his death. Since he's never been in the picture for the child, adoption or donated sperm from anyone else wouldn't matter but createing a child from a dead man that the child could know who it was he came from and his mother's obsession with his death can create complicated psycological issues and unnecessary family rifts.
She didn't even decide to have the child without encouragement despite having the funding and help, she made the thread to see whether she should respect her late fiance's will or not. So I find your wild assumption disgusting frankly.