I.G.
Please don't shame her. She will only start getting better at lying to you and she will start hating you. Shaming a kid into anything is rarely effective.
I would just keep reminding her each and every time she uses the potty - but not in front of others. When she excuses herself just give her a little "don't forget to wipe and flush".
Sometimes you just have to be a broken record and it will be a while before you see results. Parenting rarely provides quick fixes.
My DD is 5 and often "forgets" (or is too "busy") - I don't think it's a big deal... they will eventually get it.