If you have the Get to Work expansion pack, she could just be regular sick. If that’s the case every once in awhile a thought bubble of a medicine bottle will appear over her head. To get well: click on a computer - order - purchase medicine. The medicine will appear in her personal inventory. Just have her drink it and she will be all better ?
To build up: in build mode, in the top right corner right next to the light bulb button you will see two arrows, click on the one pointing up to go up a floor. From there you can add walls on top of your existing structure to make a second floor.
Carl’s Sims 4 Guide has a ton of helpful guides for new simmers. Here’s his guide on building help: https://www.carls-sims-4-guide.com/tutorials/building/houses.php