In my opinion, a person with these behaviours who does this sort of (alleged) crime would be seeking the thrill of playing God. They experience a rush of transcendence from having the power to end a life. They experience further thrills from the ongoing deception and ability to get away with it - duper's delight. They escalate as they need more and more stimulation to get the same level of thrill, and to achieve this, they increase their frequency of attacks and/or their risk-taking behaviours.
If LL is guilty and this is her motive, then her apparent sympathy/attention seeking from her friends and family after the deaths of babies could just be a cover to make herself look like she cares and has normal emotions.
I agree there is nothing to suggest that LL could be attracted to any sort of heroics, which would discount Munchausens by proxy for me.