The tool `eqn`, which she wrote (joined by Brian Kernighan) is an "ancestor" of TeX: The mathematical syntax of TeX (design started 1977) was based on eqn (1975). For example, the eqn paper (https://research.swtch.com/eqn.pdf) has the expression

    sum from i=0 to infinity x sub i = pi over 2

which would have been entered as something pretty close to that in the first draft design of TeX (the second draft introduced the backslashes), and today as:

    \sum_{i=0}^{\infty} x_i = {\pi \over 2}

and you can see the evolution. The Wikipedia page has more examples (https://en.wikipedia.org/w/index.php?title=Eqn_(software)&ol... ). Knuth credits Lorinda Cherry explicitly a couple of times in the first draft design (https://www.saildart.org/TEXDR.AFT[1,DEK]):

> A special syntax is used in formulas, modeled on that of Kernighan and Cherry, Comm. ACM 18 (March 1975), 151-157. For example, ``sup 9'' in line 41 specifies a superscript 9, ``sub {n+1}'' in line 74 specifies a subscript n+1.

and in the last page/paragraph:

> To conclude this memo, I should explain how TEX is going to work on math formulas. However, I will have to sketch out the code in more detail and it is only fuzzy in my mind at the moment. […] it may be necessary to build the parse tree first as Kernighan and Cherry do.

(Yes indeed TeX builds the parse tree first, as we can see from the second draft: https://www.saildart.org/TEX.ONE[1,DEK] )

The eqn system was a pioneering and capable one: although Knuth did not use any of the code of troff/eqn as-is (not sure if it was available to him; in any case he was targeting "book" quality), clearly it influenced the design, and I imagine it inspired him about what was possible in the first place. Even after TeX became widely used, there have been some math books typeset with troff and eqn.

Reading about Lorinda Cherry's other accomplishments like `typo` and the Writer's Workbench, it's clear we've lost someone who was a pioneer in multiple respects.