I would cut out the feeds altogether at night.
When she wakes up. No lights, no talking, don't pick her up and just settle her by patting her to sleep.
My bub went through the same thing. Once they realise that you aren't going to talk, play or feed them when they wake up, they work out that there isn't much point waking up. I have this great book that I used and had my bub back to sleeping through in five nights. If you want a copy, just send me a private message with your email.
Not the case here at all!! We tried the quiet time, no lights, very little talking, no playing & it didn't work. My son just wasn't a big sleeper, some babies / children / adults are like that, my husband isn't much of a sleeper either! He started to sleep through the night around about when I got pregnant again 6 months ago, but then I was waking up myself

As for what are you doing wrong - NOTHING!! Like I said, some people just aren't great sleepers. I noticed though the times you said were 12 & 3am, do you think she might be getting cold? Maybe snuggling with mummy & having a nice warm feed is warming her up enough to sleep & then she gets cold again? Zander was waking a bit the last two weeks because the night was cool but when we put him in bed it was still warm. I just put him in his winter jammies & we're all fine again.