L.S.
You're not doing anything wrong. She's going through something and this age is notorious for sleep regressions/issues. She may very well be teething or going through a growth spurt. At this age, I found co-sleeping to be a big help. You may want to try hylands as suggested. If it's bad enough though, only Tylenol or Motrin really do the job at night. If it's a growth spurt though, she needs to nurse and you might try cosleeping if you're open to it.