Melannie Gregersen breaks down a text structure that works: open with "Random thought!" then give a specific, personalized compliment about something unique she does. Specificity signals you actually pay attention, which makes her feel special and more likely to respond.
The next text is a compliment with a twist. The twist makes it a little more fun and playful and exciting. Something like, "Random thought! Have I ever told you how cute you look when you insert some unique thing that she does?" That right there is definitely going to make her day. We all want to know what unique things about us make us interesting and intriguing and adorable. Making it personal and specific shows that you're paying attention, and she is definitely definitely going to notice that. So again, something like, "Random thought, have I ever mentioned how cute you look when you fill in the blank?"
