As far as I know without forcing advance in quest(breaking doors) there are 2 ways to do this. First one involves perk pet pal :
talk to a dog near Jakes grave, dig up Jake, talk to dog(if he can sniff Jake scent from other stuff), go to digger, confront him, he tells you 4 suspects. Steal Evelyns coat or scarf,use the dog to sniff it, go to healers house, talk with him, get a key, go to her house, then her lair

and without the perk pet pal :
Find the 4 suspects. Go to wife house, to cellar, find bloody dagger, the perfect murder and some key. Go to king crabs inn, to the room where Jake was killed, open the chest, take a love letter, go to the legion commander, tell him what you find, arrest Jakes wife, speak with her in her cell, she tells you it was Evelyn, go to Healers house, speak with the healer, loot her pounch, go to her home, go to secret lair, kill her...aaand its still not done laugh