YABU because this lady did not imply anything of the sort to you, you've made that up.
She told a group of people about a parenting choice she has made - "As part of a discussion about choking and cutting grapes for small children, one lady said she also wouldn't be giving her daughter raw apple or carrot pieces until she was 5 years old for fear of choking."
Someone (you OP?) then turned on her and called her overly paranoid. She then explained her own reasons for her own feelings and actions - "When she was then told she was being a bit overly paranoid. In response she agreed, but explained it by saying that it took 11 years of trying and 2 rounds of IVF to have her daughter, and she wasn't willing to take any risks at all."
She didn't imply anything, she didn't say her own child was more precious than yours. She explained she has a particular fear which seems to have come to her because of her past experience. She did not say this - "Kind of like, "Oh well you can afford to take risks, you've got three kids, and anyway, you if you lost one you could always have another. This is the only one I've got and will ever have so I need to look after her more." - you made that up in your own head.
I actually have had people tell me, when two of my babies died within the space of eleven months of each other, that I could always have more. I know from personal experience that you can never replace a lost child, that's a terrible thing to say to a person. It's not true, and it's a fucking awful responsibility to put on the child who comes after a loss, to view them as a replacement or a bandage to fix the old wound.
And not all parents who lose a child can conceive again either. After two losses, we have one DS, if anything happened to him now I couldn't safely conceive again. It's not something anyone should say to anybody, but some people do say it.
The difference is, this woman did not say or imply that to you. She told you she was worried about a choking risk, got called names for it, admitted she knows she probably is a little paranoid and tried to justify herself and her insecurities when she probably felt under attack by you and your group.
And then you made up some nonsense in your head about her implying that her child was more precious than yours because you can have more.
Whether you or anybody else agrees with her about the food she lets her child eat or not, every single parent makes decisions like this all the time, regardless of how many children they have or how easily those children were conceived.
I know you said you understand that "that sort of experience" has an effect on people but I don't think you really do understand.
You just seem really judgemental about her and others in similar situations who are choosing to parent differently to you.
Plenty of people who have never had a fertility issue or never lost a child still feel anxious about their babies and children, and are careful with what they eat or what they do or don't do.
So when you say this - "Er, no every one of my children is as precious and important as yours, it's just that in life you have to take risks and eating apples is a risk I'm prepared for them to take." - you are not replying to anything she said to you or anything she implied. All you are really doing here is saying is that you make a different choice to her and you're judging her for her choice but justifying it by saying her choice implies your children have less value to her.
Do you think it's fun to be an anxious parent? This woman probably hates feeling so anxious but it's what her personal experience had brought to her. When you or someone in your group called her paranoid you say she agreed that she probably was. Does that really sound like someone who is claiming her child is more precious or someone who knows her experience has filled her with fear, which she recognises but can't help? Can you really not understand what she was saying and feel some compassion for her?
Not every parent who conceives through IVF will share that particular worry but you made an anxious person feel worse by calling her paranoid, then came on here to rant about something she did not say, claimed to understand her feelings, and then sneered about wrapping "oh so precious children" up in cotton wool.
So yes, YABU.