right, because forgetting your mistakes means you won't make them again. Diana doesn't think ahead much. Good sequence.

Exactly, I thought that would fit a klutzy personality like hers and at the same time would give me a nice reason for how she keeps transforming girls in more of my stories in the future. ^^

And thank you, glad you enjoyed it! :)

How above average intelligence are we talking? Like she can make fires with sticks?

Oh no, definitely not. XD That's why I described it as the above average intelligence "of a common fox". ^^
On the spectrum of fox intelligence, she'd be around the maximum one could hope to expect from a fox. Exceptional for a fox but incomparable to when she was human. And it's not like her intelligence is unique or anything, exceptional yes but not as if some other foxes couldn't have the same smarts as her. :)

At least she is happy to being a non anthropomorphic fox 🦊

Reading the story again has made me develop a bit of a headcanon of my own about this, where I think another aspect of the spell overlooked was that it effectively stopped Allison's aging as well, this a part of the "forest's will."
After about a hundred or so years, once the fox population has successfully stabilized, the forest (based on the line "The forest was in need of female foxes and the spell I came up with was a perfect answer to fill that gap, the fact you stated your approval so many times, no matter the method, made the spell that much more potent once I'd cast it. I've already tried to reverse it, the forest is not giving up on you anymore.") finally releases its grasp on a once-again pregnant Allison, almost ready to pop with another litter, and gives her back her humanity, along with memories of time as a fox intact.
Allison returns home to find that while so much time has passed and everyone she knows is pretty much gone, some of her great nieces & nephews and other descents of her relatives are operating the now very lucrative hotel she was hoping to save when she foolishly went into the forest a century ago. While some say she bears a passing resemblance to the girl who disappeared just before the famed savior vixen appeared, no one recognizes Allison.
Feeling like she no longer belongs in the human world, she returns to the forest, where she meets a protege of Diana, the witch who accidentally changed her, and convinces her to turn her back into a fox once more, for good. The protege reluctantly agrees and casts the spell, but the spell sends Allison into labor, causing her to give birth as she transforms, her three daughters born as she shifts being mostly human but with minor fox traits such as ears and tails.
After Allison once again becomes a simple vulpine and runs off into the woods, the protege decides to raise the three girls, who end up becoming the forest's guardian fox deities.

Parts of what you've cooked up is actually planned for the sequel. Although while the forest could theoretically give up its grasp on Allison the spell wasn't intended to stop working once the forest does (the reversal spell didn't 'linger' or anything it was simply dispelled), so unless Diana returns in a 100 years to cast the reverse spell anew, there's no trigger to initiate the reversal. Which Diana can't really do because she stupidly decided to erase her own memories, so Allison is stuck as a fox. ^^'

But because you made the effort of typing your interpretation, I'll drop some infos on what I've planned for the sequel. ;)
What the spell did do was increase Allison's lifespan. It's not that her aging stopped altogether but it slowed down considerably. Based on kitsune mythology, once a fox reaches a high age their tail might split and they turn into a Kitsune. That's what's going to happen to Allison, giving her a Kitsune-form and making her able to change between full fox and Kitsune. She won't regain any of her human memories though, all of her memories are gonna be from her life as a fox, nothing from before except for maybe some hazy afterimages and she doesn't really care about those memory fragments as it all pales compared to a century of fox memories. :)
Btw, her Kitsune change is going to happen shortly after she's delivered her umpteenth litter, so she's going to nurse and care for them in both her full fox and her Kitsune form, depending on the situation. ^^

No half fox half human offspring though. The species is decided at conception, so even if SHE turned Kitsune before the birth, the offspring would remain unaffected by HER change. :)

Then I'm gonna have a time skip of a few years and Allison will be guardian of the forest within a shrine/temple dedicated to her (with her last litter growing up to become her retainers and messengers at the shrine) and she's going to meet a girl that she's going to turn into a fox. About how and why she does so and how their interactions are going to unfold I'm not gonna detail yet. ^^

So…. How is that sequel coming along?