Just as a follow-up, my boss's Mac runs like crap now. She keeps complaining about it. In fact, I'm almost expecting her to start blaming me if this goes on for too long.
IIRC (don't use Apple's calendar app), you can choose what calendars to display, check the prefs.
First, thanks for the help.
Her calendar mysteriously started to work properly this morning, thankfully.
No, 10.11 has much better memory management. However, a couple of thoughts: sometimes the upgrade doesn't catch everything that's incompatible— had a VMWare Fusion driver kick around too long that was causing huge Spinning Beachball of Death problems and UI freezes— and sometimes some old preferences get carried forward that shouldn't.
Troubleshooting is a matter of squinting at the Console log just after it's been slow and then googling the likely-incomprehensible robot barf.
I suspected that was the reason. Honestly, it's either that or her hard drive that's failing, but since it was working just fine prior to the update and the disk check utility didn't detect any problems, it's got to be some old piece of software or driver.
The thing is:
1) I'm not sure I would be able to read the console log, which you so adeptly described as "robot barf"
2) Her computer is generally slow, so it's not like I can pinpoint a specific time or event that would help me identify the issue(s). For instance, her mail takes a second to be displayed: first the header, then the message. And from what she told me, it took the computer a good 25 minutes this morning to fully boot (i.e. getting to the desktop and having everything work normally)
Also worth spending time in a new account on it to see if it's magically better, which points to problems in her hidden library folder ( ~/Library/ )
All of that is stored in /Users/[her_account]/ and is easily backed up (if its not already!) and restored.
I'll have a look if I can.
Do you think she could just take her Mac to an Apple Store and have it fixed? She doesn't know anyone who's really good with Macs. In fact, I'm probably the most Mac-savvy person she knows, which is sad: I've never had or worked on a Mac.