Welcome to Yorkie Talk. I think you are going to have an uphill battle changing a behavior (the tongue baths) that has been going on for years. It might not be worth upsetting their happy, friendly routine.
Also, your little girl may have what is called a cotton coat (as opposed to silky coat) and that could be partly why it mats and breaks so easily. If that is the case, I would definitely recommend keeping her saddle short and allowing her to enjoy her tongue baths from her buddy.
If you still want to grow her out, you could use any dog tshirt to protect her hair from slobber, although clothing often causes matting. Show exhibitors use a silk wrapping jacket, but their dogs also have their hair wrapped up in multiple tiny pony tails.
I would love to see pics of your pooches. They sound like a really cute pair.
