|Left: an example of a social boundary demarcated by a boundary line sign on a barbed wired fence, which visually exemplifies the boundary problem difficulties in attempts to quantify societal "boundaries" in thermodynamic terms, in terms of work, energy, and heat crossings or closedness or openness aspects. |
Right: a van't Hoff equilibrium box (1886), build and by Danish physical chemist Jacobus van't Hoff, used to calculate the work done when certain chemical species cross a semi-permeable membrane; such as could be deduced for when say a Mexican species of person crosses illegally (or legally) into the American system across the semi-permeable boundary of the US border, the work cost of which typically amounts to several thousands of dollars per smuggle.
In basic thermodynamic calculations, in a piston and cylinder or in reaction calorimeter, etc., the "boundary" is visually discernible and precisely quantifiable. In applications of thermodynamics to the humanities or lower animal forms, the issue becomes more complicated because in many cases, e.g. Mean girls example, the so-called "social boundary" is not something tactile that one can put one's hands on, such as the wall of a glass beaker or the wall of the cylinder of a piston, but rather a distance of space around certain people (e.g. personal space).
In the famous Jane Goodall chimpanzee war, to exemplify the difficulties in having to discern thermodynamic boundaries for social systems, the divisional "boundary" between the two warring factions, in this case, was but a region of forest near a large rock formation.
In 1989, American chemical engineer Linus Pauling in his criticism of Austrian physicist Erwin Schrodinger's 1943 "life feeds on negative entropy" postulate (see: Note to chapter 6), though he doesn’t seem to specifically mention boundary, per se, he does criticize Schrodinger for not defining the boundary: 
“Schrodinger’s discussion of thermodynamics is vague and superficial to an extent that should not be tolerated even in a popular lecture. In the discussion of thermodynamic quantities it is important to define the system. When he is writing about a change in entropy of the system, Schrodinger never even defines the system. Sometimes he seems to consider that the system is a living organism with no interaction whatever with the environment; and sometimes it is a living organism in thermal equilibrium with the environment; and sometimes it is the living organism plus the environment, that is the universe as a whole.”
In 1990, American social entropy theorist Kenneth Bailey spoke about the "boundary problem", discussing ideas such as boundary analysis and entropy breaks; though his presentation is largely marred by recourse to information theory. 
In 1996, American economist Julian Simon, in criticism of the economic thermodynamics theories of those including Nicholas Georgescu-Roegen (1971) and Jeremy Rifkin (1989), he comments on this difficult boundary issue in saying that: 
“It is quite unclear where the boundary should be drawn for discussions of the quantity of energy, or if there is any relevant boundary.”
The following are related quotes:
“Boundaries pose a problem for sociology.”— Richard Adams (1988), The Eight Day (pg. 143)
● Boundary surface
1. Pauling, Linus. (1989). “Schrodinger’s Contribution to Chemistry and Biology”, in: Schrodinger: Centenary Celebration of a Polymath (§18, pgs. 225-). Cambridge University Press.
2. Bailey, Kenneth D. (1990). Social Entropy Theory (terms: "boundary problem", "boundary analysis", pg. 18-19; section: Boundaries, pgs. 157-62). New York: State University of New York Press.
3. Simon, Julian L. (1996). The Ultimate Resource 2 (ch. 4: Grand Theory, section: Entropy and Finiteness: the Irrelevant Dismal Theory, pgs. 77-83). 1981 1st ed. Princeton University Press.