It has nothing to do with strength. It has to do with the center of the gravity. Even if you would create a solid sculpture like this from the mold steel:
so her hand would be connected with his neck super-strongly, this sculpture would still be not able to hold on her feet. It would still topple.
But of course, this all is said in assumption, that she has a normal human weight, comparable to the weight of the guy (and, correspondingly, in the case of the sculpture, that the sculpture is made from the homogeneous alloy). If she would have a weight >> his weight, like, Idunno, 1 ton, then, of course, their center of gravity would still be between her feet, and they would be able to stand like here.