It is really hard not to doubt ourselves when things suddenly change.
It really is quite normal, though, for babies and toddlers to need help to sleep. Sometimes the best thing to do is just whatever makes things easier for you as you wait it out. They do all get there eventually, it just takes a bit of time. And if she's teething or has anything else going on - developmental leap, illness, separation anxiety - then 'training' isn't likely to work even if you were inclined to do that.