YANBU at all
I had one artificial insemination attempt a couple of years ago, which did not work and I did not want to spend money on more than one attempt so I made the choice to move on from that.
I am a (lesbian) single mother with 3 children (one already an adult so two at home) by the way
Now, actually a few years on I am thankful it did not work, because my finances are worse now, and my second child (who has multiple special needs) stopped being on an even keel and is even more challenging to parent. I would be able to manage another child yes, BUT in my current circumstances not ideal
My child would not have had a father, no. There would be an opportunity for another mother but that's really not likely. I very much wanted an open/ID release donor which is mandatory in the UK anyway, partly because I think it's the childs right to know, and partly because my adopted children have all the information about their own backgrounds and to have one child without that would not be right IMHO.
But a father is not necessary. When studies are done about single mothers, poverty is still the biggest factor in outcomes for children. Children of more wealthy, professional single mothers tend to do well, I think just as much so as children in 2 parent families. Poverty and hardship put a big spanner in the works. A child needs good male role models yes, but that needn't be a father at home.
Ah and I see the old appeal to nature rears it's fallacious head. Adoption (the legal bit at least) is not 'natural', nor is Mumsnet or this computer. Or IVF, or modern medical treatment. Cannabilism is pretty natural though....so many animals eat their babies y'know. So is aggression, murder, the least goes on. Natural and 'right/moral/good' are totally different concepts. Natural is not good and unnatural is not bad. It's a fallacy.