The growling when you reached under her belly could be discomfort - how is she if you touch her belly when she is laying on her side? It could be that you leaned over her and crowded her space (many dogs do not like feeling trapped). It could be a general lack of trust and she did not trust your intentions to pick her up. Isn't she a large dog? Why did you need to pick her up?
You might have set her up for failure with the cats. It sounds like you have made great progress over all but we might have pushed the envelope a tad. Did she have a leash on at the time? This would stiil be crucial so you have the ability to correct any poor choices and as an emergency brake to stop her from making contact.
She needs more practice with the 'leave it' drill so that as you approach her bowl to take it away she steps back from bowl. If she keeps her face in the bowl when you reach for it means that she is trying to claim the bowl and it is a red flag that she still has issues with her food bowl - it's just more noticeable with the cats.
Love Them & Lead Them,
~Elizabeth & Doug
Dog Training the Way Nature Intended