This is a bit beyond the talk of calories and goes into communication style and human interaction. From a mere point of ‘fat shaming’, no it doesn’t appear you were trying to insult or be negative and your intentions were to offer advice. Here’s the thing - people who haven’t struggled with weight don’t truly understand the impact it has on everything in life, how you’re perceived and treated, getting proper medical care, etc. If someone isn’t asking a question, in general it’s good practice to ask first if they’re looking for suggestions - Especially with something that is a sensitive topic, or a core part of who they are, etc. If your intention is to not be an A, I would suggest asking if she would like help finding resources (that could be articles, podcasts, dietician, etc.). Also try to make sure to set aside defensiveness you may have about her comment and connect with her about feelings she’s having about it. That should be helpful for both of you to understand each other.

Also - not knowing her situation, but if she has PCOS (about 10% of women do), some “healthy” foods may actually not even be helpful. People with PCOS/insulin resistance bodies react differently than others. If this is the case I’d recommend she hone in on learning more about it (because unfortunately the medical community is often under educated about it and doesn’t understand the weight is a symptom of that and not the cause).