My quick thoughts. If the message is regarding your kids, or $, or something you feel important - then respond promptly so you know you are doing your best. Anything else, don't bother with it. She may be trying to engage you and then go cold, she may want to keep you on a string, etc.
Also, save what you have to say (unless it's urgent) to when she initiates. That keeps you clear of being the pursuer etc.
Food for thought.
M:50 W:53 MR:20 D:21 S:17 S:11 BD-Sept 2015 Suspected PA Sept 2015-Confronted W & OM Dec 2015 Actually EA In house Sep:Jan/16-May 2016 W moved out:May 22 2016 OM-Intro Oct/17-On scene July/Aug 2017