Apologize for being inconsiderate. Protecting Esme is more important than rescuing someone we don't know.
New plan: We'll just kill Jenifer and some other people to make our killings look random and then absorb their memories, making it look like we're praying for our victims while we absorb their memories. That way we have to share no information with her and thus there's minimal chances of any investigation leading back to us or even revealing what we're after. Once we're out of ammo we cut our wrists to make it look like we committed suicide and jump to an animal we have prepared beforehand, hide for a couple of days and then jump back to Esme's library. The small delay hopefully helping us evade pursuit just in case they manage to track us anyway.
Of course, that's assuming she'll be easy to get to. If she's in isolation/high security/whatever we might have to come up with another plan. We can decide once we have the guard's memories.
As for what we're looking for in her memories, it's these things:
*Who Kelly was as a person. We might have some of his memories, but we aren't sure. We're only certain we have fragments of Esme's memories and even those fragments might be romanticized by nostalgia. Having the full perspective of someone who worked with him and interacted with him more might help us figure out what kind of person he was and if the fragments of memory we have are real or just Esme's memories we confused for our own.
*What she did for Kelly. What Kelly was interested in. What he was researching and why. What happened to him. Why did the government go after him and his associates.
*Did Kelly kill all those people at the research facility? Was the large number of deaths the thing that attracted those huge entities and made it so that even normal people could see them? What sort of experiment was that? What was its purpose?
*The projects the government is currently researching. What are they? What is their goal? How do they relate to Kelly's previous work?
*Does she know of the location of anyone else who was working with her? Does she know of the location of any research facility, equipment we or the resistance could use or other people/items of interest?
*Does she have any dirt on the government's leaders? Something that the resistance would find useful like plans or locations of facilities?
*Has she talked to anyone else? Has she given the information we have to anyone else? Has she been approached by the government/the resistance/other organizations?
*Does she know of any really powerful government agents or mercenaries? Who did the government send after Kelly? What was their magical ability, if any? What method did they use to attack/trap him? It's highly likely they'll be coming after us when the time comes, so we best prepare for them.
*General information about necromancy. Maybe they know of some property or ability necromancers or undead have we don't know of.
Of course, we can go through her memories more thoroughly when we have more time. Hopefully she'll be useful. But with our luck she might have brain damage or lost her memories with age or she'll simply be some insignificant assistant that got caught up in all this and doesn't really know that much.