I don't see her as actually having a hoarding problem. I see the problem as a manifestation of anxiety issues (she does have an anxiety dx) as well as likely just a personal way of being. It's hard to know which is which sometimes, right?
To my way of thinking, if nobody has a problem with the mess/objects being in the house, then the hoarding is not a problem-- but the anxiety itself is worth getting a handle on. This kind of anxiety is (in our experience anyhow) the kind that feeds off being indulged, turning into a bigger thing over time. To me, the anxiety seems worth addressing (by working on the anxiety in general and by teaching the skill of throwing something out in particular).
I am untidy and always have been-- but I am very glad that my parents made me get a handle on my pack-rat anxiety as a kid, because as an adult you have to manage bigger decision-making, some of which is also anxiety-producing. This is an opportunity to build the "I'll decide and it will be okay" muscles.
DeeDee
