Dorothy Crane is one of the pillars of Whitechapel, and a very important character in Vampyr. In Chapter Two: White Coat, you will be able to decide what to do with her. Doing the mission called Blackmail in Whitechapel, you will reach her facility, where the decision can be made.
Spare the woman, but have her give up on blackmailing Lady Ashbury. This is a very good solution, since the woman is unharmed. This is the only variant, where Dorothy Crane is left alive. That's pretty important, since Dorothy sells the formula for the last tier of meds.
You can drink her blood right away and kill her. This will give you quite a lot XP, but remember you're killing the district's pillar. Loosing Dorothy will severely impact the whole district - people will fall ill more often.
You can also charm her - she won't be a bother anymore for Lady Ashbury. Unfortunately, this also makes Dorothy loose her mind and vanish the next night. You can then go back to her facility to find her transformed into a 24-level Skal. She's quite strong and able to perform a gas attack - after she's dead, you will be able to take her key and open the nearby chest, where you will find some new meds.