After about three attempts I have finally completed this challenge.

Meet my sim, Ashleigh Wilde

In my first attempt I gave her the traits Creative, Childish and Cheerful. Things were going rather well...

Then I realised I had broken the rules rather thoroughly...

Second attempt I changed her traits to Creative, Childish and Loves Outdoors. Which was just as well because she wasn't going to be able to go inside until she had completed the challenge.

Again things were going rather well...

And I went to bed. When I woke up I lay in bed for a while thinking about how I would build the mansion. Then I got up, went to the computer and found myself looking at the logon screen. There had been a windows update during the night and my computer had reset itself.
I hadn't saved my game before I went to bed.
Third attempt was similar to the second except I started building the mansion on the other side of the wall earlier on. No furnishings, just walls, windows and doors. I made the walls extra high so I could add more paintings. If Ashleigh produced a painting that was the same as the one on one of the walls I sold the one that was lower in value. So I build up the value of the property that way.
She prepared single serves of salad for herself until she maxed out her cooking skill and then I bought her a stove. She then prepared single serves of Pasta Primavera until she maxed her gourmet cooking skills. Her main source of fun was the Easel and I can't remember whether she maxed that or cooking first.
After she completed the writer aspiration she did the Prudent Student stage of the Renaissance Sim and Nerd Brain aspirations so I bought her an observatory for her to work on her logic skill.
It was a bit of a tight squeeze....

But it was rather a nice source of space prints.
So the skills she maxed were:
Cooking
Painting
Gardening
Gourmet Cooking
Writing
and Logic
The aspirations she completed were:
Painter Extraordinaire
Bestselling Author
Mansion Baron
and Freelance Botanist (16 milestones in total)
Individual Milestones
Tone Deaf (Musical Genius)
Readily a Parent (Successful Lineage and Big Happy Family)
Aluminium Chef (Master Chef)
Going For Not Broke (Fabulously Wealthy)
Prudent Student (Renaissance Sim and Nerd Brain)
It took her 64 days. So
Starting score 100
Skills Maxed 60
Milestones completed 105
Time spent -63
-----------------------
Total Score 202
Rewards she used were
Creative Visionary
Steel Bladder
Never Weary
Savant
and Insta-Lean (because eating all those grilled cheese sandwiches she made for Aluminium Chef were not kind to the figure)

She now has a way out of her enclosure...
