feeding to sleep isn't 'wrong'. It's just not for everyone, long term.
So at nine months you would do PUPD which at this age essentially amounts to trying your best to settle her in her cot. She may not seem to calm or be comforted by you at all, but it's not like CIO because you are there reassuring her. But you should expect some pretty hard crying. That said, you can also expect to see pretty quick progress, so if you are consistent you should be all done with sleep training within a week.
To give it it's best shot, have a plan for when/if you will feed overnight, so that you know before you go in to her whether you are going to feed or settle her without feeding. Don't do PUPD for an hour and then feed, yk? That's just confusing.
And check your routine is age appropriate, so you're not trying to sleep train a baby who is over- or under-tired:
Average A times- BOOKMARK ME! How does that sound?