Having a bad day

So I’m an assistant manager at a small retail store. We are already short staffed so Im stocking the pet food today and this woman. (55 ish) walks up and tells me I have a very pretty face ( I was flattered, thought that was it and said thanks) but then she say but why are you so fat. Ugh usually I’m not an emotional person but all I could do was walk away. I went and cried in the restroom for a good 20 mins trying to pull myself together. This woman has ruined my whole day. I have lost 25 lbs in 3 months but of course she doesn’t know that