Outdoor playtime is only for kids that are cooperative and get themselves dressed. If she does not dress herself and walk herself out she sits on a bench/chair and watches the others play.

Inform of this tomorrow morning and remind her right before you start getting dressed. After that it is 100% up to her. If you need to help for ANYTHING (that you know she is capable of) she forfeits playtime. Be really firm the first many times so she has to sit out and feel the consequence of being uncooperative. She'll eventually learn that it doesn't pay to be this way.