I had this problem too, or similar. I co-slept with both DS1 and DS2. DS1 till he was about 15-16 mths. He was not a problem - he always slept in his cot for the first few hours of the night, then came into bed with us when he woke up. With him, I put a futon in his room, and to begin with, when he woke up, I brought him into the futon (rather than our bed). After a week of that, when he was used to staying in his room, I started putting him back in the cot after he fell asleep in the futon. He would wake up a lot more often, and it was a tough week to ten days, but then he started getting used to it and staying asleep longer in the cot. Finally, he stopped waking up, and I stopped sleeping in his room at all. It was easier for me though, as DH and I took turns sleeping in his room, so each had a good alternate night's sleep.
With DS2, intended to follow the same pattern, but he went through a phase like your DD, where he would NOT go to sleep in his cot. He was about 15 mths. So, for a while, I used to bring him down to the living room, turn the lights very very low, and let him crawl around in his sleeping bag (but didn't play with him.) When he got tired, he would come and sit on my lap and finally fall asleep on my lap. Then DH would carry him up & put him in his cot. He would wake up several times in the night, and each time have to sit on my lap in his room to go back to sleep. Some nights I would fall asleep on the chair in his room (with freezing cold feet). Occasionally I would end up bringing him back into our bed as desperate for sleep. Couldn't alternate with DH as DS2 would only have me. Thought I would die of tiredness. But, after 2-3 weeks, I decided to rearrange his room. Made it look much nicer and cosier, with a soft light in one corner, and magically, that night, he was happy to stay in his room and fall asleep on my lap there (rather than coming down to the living room). Breakthrough! Another week, and he was not waking up so often. Another week, and he was (mostly) sleeping through, plus if he did wake up, going back into his cot very quickly. I feel like a different person. Incidentally, I also realised with hindsight, that through all the time that DS2 was resisting going to sleep, he actually had a chain of colds/coughs/teething. Might that be an issue with your DD at the moment, so she is wanting extra comfort? Once DS2 was healthy again, that made a big difference.
Sorry for the long post, but I really feel for you - esp since you are on your own, so no-one to give you a break. Small steps. Maybe start with having her fall asleep in the bed with you, then transfer her to the cot. Perhaps she is no-longer finding the travel cot very comfy - can you get a more comfortable cot for her (I don't think travel cots are recommended for sleeping in all night every night). Let us know how you are getting on.