In Sleep He Sang To Me
((of course, Shirley isn't much of a fighter when Transformed, either...))
Shirley quickly weighs the situation; while letting Moriarty escape would be a bad thing for sure, there's simply a more pressing matter at hand... even though it's one she isn't really qualified to deal with. What should I do? What CAN I do? Then, she notices one thing; the way monster is positioned, it won't take much of a push to throw it completely off-balance... of course, "much push" is relative to the target's size - on the other hand, jujutsu is the style that favors speed and technique over size and weight. With newly gained confidence, she ducks under the monster's head and rushes forward, with intent to slam into one of its' legs...
And then, something clicks in her mind, and she sees the world around her with crystal clarity, almost as in a slow motion; and her previous idea of "push it off-balance" turns into a detailed calculation of the optimal point for applying the force, and the added twist required to maximize the effect... (and she even has some spare time to appreciate the outfit she suddenly finds herself wearing - it is so similar to what she got when she once tried to imagine herself in Holmes' place... except the current one is much more elegant, somehow. Well, it IS a dream... so she dismisses it as no more weird than dreams in which one suddenly finds herself undressed... and much less unpleasant.)
As for Moriarty... no matter where he runs, she thinks with certainty that surprises herself, we'll finf him anyway. I'll find him.
((The idea of experiencing the fight in bullet-time is taken, of course, from Downey Jr.'s version of Holmes, though I'm not sure whether Shirley actually saw it; she's more into classic interpretation.))