Yes! It was Laurie from Little Women after Jo refuses his proposal.
Mycroft started to follow her, but Sherlock grabbed his arm. "Let her go."
Mary put out a placating hand. "Won't you let me talk to her? I can explain that you were shot, that you didn't just avoid her-"
"Fine," Sherlock said wearily. "I'm not about to argue with a pregnant woman in her last trimester. Hormones and the like."
"I have a flat here," she ventured timidly. John looked shocked, Sherlock nodded. He'd probably deduced that the first time they met. Oh well. " Just a studio. I kept it when I was running missions. I think I'll bring Lissie there. Here's the address."
Mary hastened after Lissie's haughtily retreating figure. As she drew closer, she noticed that the girl, for all her brave words, was crying.
"Lissie. Will you come with me? I've a flat here, and I'd like to talk to you. Just us girls, y'know?" She smiled kindly and wondered how Lissie would react to the news of her shooting Sherlock.
The girl hesitated. "All right."
Soon they were sitting on the sunny little balcony of the flat, drinking tea out of enormous mugs.
"I have some things to tell you," Mary began, "And I wondered if it would be easier to let you make some guesses first. To begin with, who am I? What do I do?"
Lissie blinked at her frankness, but sat up. "Well, you've got some sort of background - military or espionage, maybe? You always sit with your back to a wall and look for exits, and you've got a good memory.
Sometimes, when I first met you, I had to say your name several times before you answered, which indicates it's an alias. You seem familiar with lots of cities, and..." She trailed off. "I don't really know. They're just guesses. I'm not like Sherlock."
"You're rather close. I do have an espionage background...in a way. Let's begin when I met you. John and I had just married, and Sherlock had found you. Then you were kidnapped the first time and returned. I was about four months pregnant. Then you were captured again, two months later, and returned to school. Shortly after you returned to school, I..."
Lissie saw her hesitation. "You're the only who's explained anything so far. You could say that you helped Moriarty and I would still listen."
"Good. I'll be blunt. I was on a mission of sorts when Sherlock and John stumbled in on a burglary. They didn't know about my background- Sherlock had an idea, but-"
"A burglary?"
"It was for a case. Now, I was assigned to my...usual job and was in the act of carrying it out when Sherlock stumbled in and stopped me." She closed her eyes briefly, and Lissie could tell that while Mary was capable of being terrible she was not yet hardened enough to enjoy it. "I shot him."
"You what?!"
"I shot Sherlock. Rather badly. He nearly died. It was awful, but had to, Lissie." She place her shaking hands on her stomach.
"Why?"
"I didn't want to. I had to. I did the only thing I could do, then I called an ambulance and ran out."
"You're practically a murderer!"
"That's my job description."
"I want to hear this, so I'm staying. But I trusted you, Mary!"
"I've let down lots who trusted me, I'm sorry to say. You aren't the first. John was furious, of course, but more hurt than anything else. I'd lied to him so much...Sherlock made a full recovery and reunited us at his parent's for Christmas."
"Just like that, it's over?"
"No. John is a wonderful man, Lissie. He forgave me, even threw a flash drive containing my darkest secrets into the flames. But a man had found out about my career and posed a terrible threat to us.
Sherlock stole Mycroft's laptop to use as a bargaining chip. He and John then went to see about the man - Magnusen. Things went a bit awry, and in the end, Sherlock realized the only way to keep me safe was to eliminate Magnusen. So he killed him - thus the stolen secrets and murder. Obviously, an alert went out for Sherlock, with police being sent to find him. He couldn't possibly have left Magnusen's in that time, of course, and was found there and sent to Eastern Europe."
Her eyes welled with tears. "Don't you see, Lissie? He did it all to save me. You're a Christian - you know about grace and how 'while we were yet sinners Christ died for us'? Well, in his own, albeit fallen way, Sherlock saved me from an earthly hell - a fallen man, yes, but still for the side of the angels."
Mary placed her hand on Lissie's, and she didn't pull away.
"If you have to hate someone, blame someone, it's me. I shot Sherlock. I lied about my past. I'm the one he killed for, stole for - well, John too but it wouldn't have happened if I hadn't lied.
Lissie, Sherlock's just a man trying his hardest to be both father and mother. Yes, he could have made more effort but you see he was shot and then wrongly imprisoned. You can hate me it you want. But love Sherlock."
"Oh, Mary." Lissie whispered. "Thank you for telling me."
They were both silent.