I already shared with you that my cat was a bit sick, was throwing up a lot, having diarrhea, drinking lots of water and didn't want to eat the food I was gaving her.

It happened that I found out, a lady who lives next to me is feeding her.

Isis (my cat) every morning starts to meow like a lot and really loud, and I open the door for her (she likes to be outside very much). Today, my dad followed her to our neighbors house, and give her a slap in the bottom (I'm not an English native speaker so I'm not sure if this is the right term) so she came home.

All of the sudden, my neighbor got out of the house and screamed with my dad saying that slapping her is not correct and etc (I have Ísis since birth and taught her with slapping when she messes up, but nothing serious of course. Things like climbing to the counters and to the table etc).

My dad ignored her and went to his business. While walking away, he turned around and saw the lady picking Ísis on the lap (she carried her..) and feeding her again.

The food stays there during all day and night in the sun. This is potentially the origin of diarrhea and throwing up and etc, bc when I don't let Ísis go outside, everything is fine.

What to you think about all of this? Which should be the best approach for me to talk with this lady?

Sorry for the long post in the first place, but we are really concerned with all of this.