I actually wrote a college ORP on this strange but adorable topic and this was part of it. So this is my view: She was diagnosed at 30. It's likely that sensation would be lowered over time especially at the site of injection however, it's unlikely she'd use the entire soles of her feet as she was an avid dancer and diabetics, on average, tend to use 3-4 different areas over time, usually staying away from sensitive areas like the feet or hands. Also diabetes, age, callous and injection sites are all reasonable factors to contribute to becoming less ticklish over time. So all in all, I don't think the nerve endings in her feet would've been destroyed but it is possible her feet were less ticklish than say, her sides, by the time she was older.