well, at least it's an E175 so you didn't end up in middles.
i haven't experienced this with Delta before, but plenty of times with UA and AA.
hopefully 12C or 13D will be willing to make a switch. otherwise, this seems to be LGA-ORD which is a fairly survivable flight to be separated from someone who is not a conjoined twin.
maybe you'll get a nice FCM offer.