That sounds hard, especially having two kids to think of.
My son could not be left alone at sleep time till he was about 2, and from then we found he gradually got the point where he was happy to go to sleep by himself (following a rather intensive bedtime routine, I might add). By 3 he was telling his daddy to go away when he was ready to sleep
We did nothing to push this and I think the main thing that helped was time. It really is normal for young children to need help to sleep. At this age, though, you may be able to tweak things and perhaps gently encourage more independent sleep, if she's ready.
What happens if you leave her alone briefly? Can you negotiate sitting by the bed, rather than lying with her? Those first little steps are often the most difficult - do you have someone to help with DD2 to give it a go for a few nights? You may find that if you can get her to sleep sitting with her, rather than lying down (which might take a while), that the next step - just ducking out quickly to go to the loo or whatever - will be easier, and from there it's not such a stretch to her going off to sleep on her own.
Has she finished teething?