The chinese think that 8 years' age difference is perfect.
Call, don't text.
Just read this to her: "Hey, this is Hellfish from the gym. I'm sure you get a lot of offers from guys, so I'll just remind you I'm the huge, handsome body builder with the green tank top on who asked if you'd join me for coffee yesterday. Thought I'd call and ask when might be a good time for you. If you have time, I'd love to turn that coffee invitation into a dinner invitation...or lunch if it's more convenient."