I can definitely recommend a three hourly routine (in the day). There are lots of reasons why it should help your daughter sleep longer at night.
It'll ensure that she is getting enough to eat during the day so able to go longer stretches at night, it'll get her taking full feeds rather than grazing day and night, which can be what demand feeding leads to, and will also ensure she gets good daytime naps, which will help with nightime sleep.
It'll be harder introducing the routine at her age than if you'd started from the word go, but should be possible. Its important to feed at the same times every day - 7am, 10am, 1pm, 4pm and 7pm, and most important of all is a dream feed between 10pm and midnight (we feed my DS at 11pm) as this is what gets them sleeping for a longer period at night. There's some flexibility with the timing of the feeds, you can move them 15 mins either way. There will be times when she is bawling because she's wants feeding, but if you are strong (its hard) and can distract her, she'll soon get used to it as will be taking full feeds each time as she's hungry and it'll be so worth it in the longrun. So you do have to make sure she gets a full feed otherwise it'll be almost impossible to keep her waiting for three hours. If you have to give in and feed an hour early though it'll muck up the routine for the rest of the day as it'll be really hard to get back on track.
Also, in between feeds, at the same times each day, put her down for daytime sleeps in a different place to the moses basket. And have a bedtime routine that is the same every night - same time, same order of steps (nappy, bath, feed, lullaby, lights out, 'night night') - always the same.
To make it really work, I'd recommend reading the very straightforward and quite short Baby Secrets, by Jo Tantum, which is where this is all from. There's lots more help in there and I honestly can't recommend it enough.