Sometimes it may have started out as a n affection type thing, but it sounds like your dog has gone to the obsessive stage --when it comes to faces and in particular your Abby. Some may only lick faces, some may lick themselves, some may lick everything -- but when it is too much -- it is excessive licking. So, that is why I sent that link to you. Maybe this one will actually explain it better as it relates to a dog that just is "kissing/licking" faces of people and other dogs.
How To Stop Dog Licking -- Excessive Dog Licking Can Annoy - STOP Licking...
We want to think they are just kissing, but it is still licking and their licking can have lots of causes. If they are doing it to excess, even if only with other dogs and people, it can be stress related. You need to find out what is going on in your particular case. Boredom, lack of attention, just being away from you too long -- all of these types of things can result in excessive "kissing/licking." Excessive licking (even as a kiss) is the most common way dogs show their unhappiness or tension. Some just show the excessive kissing/licking upon your return. It is still a compulsion type thing. You have to be the one to decide if it is excessive or jut a normal greeting when you come in. Since you have already identified it is causing your Cavalier a medical problem, then I think it has definately gone to the side of compulsive disorder. I think you might see the idea more clearly through this link than the one I posted the first time. It really shows thta it does mean dogs who "kiss" excessively as well as those who otherwise over-lick.