Y'all matched on tinder and traded igs, it isn't creepy for you to message her - that's the whole point!
Wanna know the secret to talking to girls? The secret is that women are very forgiving. They'll forgive you for being annoying, or dumb, or awkward, or creepy, or a jerk. But the one thing they'll never forgive you for is being boring. Hence, the winning strategy with women is to always swing for the fences. Make a dirty joke, or tease her mercilessly, or just fucking ask her on a date! Anything is better than ho-hum fact-sharing conversation!
Here's the thing - right now you're all torn up over whether or not she likes you. Whether or not she is flaking on you. So what do you really want? You want to know. So send her a message where you are completely, unambiguously broadcasting your interest in going on a date with her. Then, forget about her. Send that message, just assume that she is now a dead lead, and move on with your life. And maybe you'll be pleasantly surprised.