Try this, if it works come back and accept.
If the chewing gum is one piece, place the filp-flop in a bag and put in the freezer. Frozen chewing gum can be easily pulled off.
Hope this helps.
Then try this: Take a can of hair spray or WD-40 and spray the area of the shoe with the gum. Allow it to sit for a minute or two then with a paper towel or rag wipe away the gum and the oily spray from the shoe. You may need to wipe again with another clean paper towel or rag.
Good luck, and let me know how this goes.
Thanks. I hope it works.