Wow, she is having a hard time. LOL
You can tell how much further she has to go on her aspirations if you click the star icon to the right of where it says "Painter Extraordinaire." It is right below the gift icon you clicked during this episode and got the painting trait. This star icon will allow you to view and / or change your lifetime wish.
Also, now that you can sell to a museum, choose that option because it gives you more money for each painting.
Here's a guide that might help you. http://www.carls-sims-4-guide.com/skills/painting/
I look forward to more episodes. ;)
I may re-do this challenge now that there are ghosts in the game. ;)