co sleeping will make a difference. Which is why so many people do it...without telling anyone...most of my friends co slept at one point or another and ended up with kids in their bed up until the age of 6 or 7! It is perfectly normal. You can still start a child off in their own cot and have a early bedtime for them, and bring them with you at night time if they wake. I have three kids, and this worked well for me.
The only other solution is to teach child to self settle in the day, you start with the daytime naps..so when child is getting sleepy you start introducing some sleep cues which aren't to do with touch or movement. So could be a music box, or a darkened room or a special toy you keep for bedtime (ours was a knotty rag toy). Then try and get baby to have two hour naps, so if baby wakes, resettle by putting back in cot, and repeating sleep cues, in the afternoon. This in turn gives them the skills to self settle at night. Screaming at night is awful but a bit more bearable in the day if you want to practice cueing and self settling.
Other things to check are food consumption in day..could she actually be hungry...too much milk at this age is a common problem and not enough solid food, so then they might need more feeds at night to catch up.
Also check for earache, that can again be a reason why babies toddlers find it difficult when they are lying down, but seem fine otherwise. Overtiredness can be another reason for poor sleep patterns at night, so make sure she is getting enough sleep between 7 and 7..mine needed at least two hours if not more in the day.