I think introducing a lovie is a great idea. My DS uses a muslin square (so there's always plenty of clean ones which is great for when they want to chew and suck on it!) as a lovie, he rubs his face with it and also sucks and chews on it, he particularly likes the label (I believe many LOs love labels on cloths or toys!).
If you introduce the muslin whilst feeding and cuddling she will become accustomed to it and you might be able to encourage her to self sooth by sucking her thumb whilst holding the muslin, or like you said through the muslin rather than feeding to sleep.
With regards the feeding to sleep prop. I suggest you tackle all naps and BT at once. Initially you only need to introduce a short awake time between the feed and the sleep. Even a few seconds or a minute will begin to break the habit gently. Try to keep her awake for the whole feed, if she starts to nod off tickle her feet, cheek etc, or take the bottle away. A nappy change is usually a good way to get your LO to wake up between feeding and sleeping, followed by a cuddle, a key phrase or song and soothing to sleep with shush/pat.
I suggest beginning with the first nap of the day rather than at BT. With the first nap of the day you will have more energy to help your LO through this change in habit. It also gives several opportunities to practice falling to sleep without feeding prior to the BT sleep. You never know, by BT it could be a breeze.
good luck