I get this error:

But I literally have 5,865 sP on me. Does she take into account how much I have in the bank? I've never had this issue appear and I've definitely had 30+ mil sP on me before and completed her quests like usual.

Yes, she counts sP in the vault. She doesn't count shop tills, and it's currently allowed to put your sP into a forum group bank so that you can do her quests so you could use that as a workaround (at your own risk, if you're using a forum group with other admins besides yourself; this was okayed during the last quest-a-thon and in a ticket I filed in January but with another quest-a-thon coming up soon, it could change)

Thank you for responding! That seems a little wild that she has access to my bank. I'll look into the work around, or I could spend the sP I guess?

The reason it never applied before is your account age. If you've been onsite for less than 6 months you can do Sarah's quest without an sP limit.