Well, for instance, it's okay to meet an ex-now-friend for coffee and conversation at a bookstore. It is not okay to take an ex-now-friend on a motorcycle ride followed by a picnic in the park. It is okay to make arrangements with an ex-now-friend to share the expense and work involved in arranging the marriage of a mutual child. It is not okay to still have your ex-now-friend on the deed to your primary residence and allow her to spend winters there when she is snowed out of her cabin (especially if she still keeps a picture of you in your football uniform age 20-something on her bureau.) It is okay to keep an ex-now-friend as your dentist. It is not okay to keep your ex-now-friend as your massage therapist. It is okay to send an ex-now-friend a Christmas card.It is not okay to send an ex-now-friend a valentine even just-to-be-funny.What counts as disrespectful?
These are some of my boundaries. YMMV.