The first an fourth focus on the same character Tannim a human mage working for elves and mentored by a dragon he is fun they are available in a collected volume called "The Chrome borne".
The other two in the series and I think there is third recent release are connected but feature different leads. She has a few other series as well some by different publishers.
Such as Diana Tregarde investigations which is about a witch/guardian and her vampire lover dealing with supernatural threats.