I sent the following practice suggestion to a parent/kiddo practice team who were having a rough week last week. (Come on, you KNOW we've ALL been there, regardless of how old we are!) It comes from the book "Helping Parents Practice" by Edmund Sprunger.
Designate 4 "Parental Warning Tickets" for use during one practice session. During that practice time, anytime the parent says something critical (in a very polite way, of course) the kiddo takes a ticket. Once the four tickets are used up, the parent can only make positive comments. This is a great tool for making practice a little "nicer" on particularly tough days. When she's taken all 4 cards, the parent is only allowed to give compliments on their playing. Which building upon your strengths, as we also all know, is still really helpful to the learning process.
If you try it out, let me know how it goes, even if it flops.
[You can get a poster version of the image above by clicking here!]