I don't know too what is going on her mind but girls do various things. Maybe she just like what you posted or letting you know that she still checking out on you. If she doesn't text you , then why don't you do it instead. Do you want to begin a communication with her? If you do, then you should initiate it first. There are times girls or ladies are just shy to do it, but you never know it once you tried. I don't have an ex, but when I observe with friends, some of them are liking ex's post on social media. Some just stay to be friends with them, follow them and check on their post but not liking anything. Some decided to unfriend them and to make it worst, block them so that they will not see each other. Your ex checking your post on Facebook is cool, so I think you should appreciate that.