Is it permissible for me to like Facebook pages that publish pictures of unveiled women, and would I be sinful for doing so, or for displaying pictures of unveiled female friends on my page to my friends? Am I exaggerating by avoiding adding friends for this reason? And would I be sinful for inviting an unveiled female friend to visit me?

If most pages publish objectionable content, it is not permissible to subscribe to them, follow them, or like them; because it is an affirmation of the objectionable and a رضا (acceptance/assent) of it, and it contains an indication and dissemination of disobedience. As for beneficial pages that may sometimes display forbidden things, the ruling depends on their purpose. And inviting a friend who does not adhere to Sharia regulations in her dress is not considered cooperation in sin, but she should be advised to abandon ostentatious display (tabarruj) and unveiling (sufur), and if she does not respond, it is better to distance oneself from her.