She so rarely does, not even after using the toilet or removing poo from the cat's litter tray (or after doing a full clear out). We've explained to her the health risks, but she's not a girl who cares much about hygiene much (she washes once or twice per week, although only when DW makes her).
After we told her to wash her hands, she did (or so she claimed), although the water ran for about 1-2 seconds.
We have tried in the past to get her to wash her hands, but it doesn't work. She will just say that she does, but doesn't.
I feel sick just thinking about it. Although I know some people believe washing hands doesn't matter.