I think most people who don't like having their feet touched are ticklish there but it's hard to know, especially since she said it makes her nauseous which is quite a bit different from getting ticklish.
Jenna Ortega actually said something similar in an interview I can't find anymore. I think she was asked about foot massages and said she 'can't do massages', and being touched like that makes her very mad. Again, probably a ticklish thing, but not a confirmation