This sometimes happens with spayed females, and seems to be mostly linked to the genetics of the given dog (just as some women have drier hair and skin after menopause than others, and some seem to have no issues at all).
In addition you are talking about an older dog, where you often get coat changes anyway (just as in aging humans you get hair and skin changes). Has she gained weight? Extra weight is also linked to coat changes.
Adding some fish oils and using a good conditioner helps with coat and with some dogs it makes sense to have them professionally groomed to take out some of the fluffiness.
Coat changes however are a minor and merely cosmetic inconvenience compared to the health benefits for spayed females -- any pregnancy alone has a mortality risk and this breed has a 40+% risk over lifetime of a pymometra infection in intact females -- which can be fatal and at best makes the dog very ill requiring spaying immediately anyway; plus a 25% chance of mammary cancer if left unspayed.
It makes sense to get some professional help to help shape your girl's coat if it bothers you a lot, and maybe try boosting the diet in ways that benefits coat.
If it is any consolation many of us have fine haired dogs -- particularly blenheims and rubies -- that mat badly all the time regardless of whether intact or spayed. If I go more than a couple of days without brushing out my cavaliers will all begin to mat. I find a silicone-based coat conditioner makes a huge difference and keeps coats smooth and sleek.
Incidentally the breed's coat is supposed to be long and straight -- curliness is considered undesireable -- are you sure this isn't just the normal adult coat growing out? It has taken one of my boys til age 4,5 to really have his full adult coat come in