Is it valid to use:
We will be pending for her return
instead of, for example:
We look forward to her return
In a comment. John Lawler said...
No. Pend is not a normal verb in English; the adjective pending is used to describe unfinished tasks and decisions, but it never occurs with a human subject. Look forward to (not look forward for) is OK, and wait for or await (without a preposition) are also OK.
But be careful of spelling.
If I add a comma, remove for, and assume some context, the following would be okay:
"Will you be okay?"
"We will be, pending her (some person who causes bad things) return."
Used as a standalone sentence, or without a comma, it sounds far more bizarre. But since punctuation isn't syntax, and syntax can remain valid outside of context, the following would be at least syntactically sound:
We will be pending her return.
However, without that aforementioned context, it's easy to try to interpret it as meaning something like this (I can't help but add the comma back in again):
We will exist, pending her return.
But we almost never use be on its own. It's almost always followed by something else. Only with Shakespeare's to be or not to be does it stand on its own—and that's a very specific idiomatic phrase.
This is also possible:
Approval is pending.
So, although it doesn't sound entirely right on its own, the following is also possible:
Approval will be pending (once you fill out the form).
Not only can objects or concepts be pending, but so could people in some contexts:
After fertilization of the egg, the baby will be pending.
So at least in theory (but not in any real-word use), this is at least syntactically sound—even if not very idiomatic:
We (members of an emergency medical team) will be pending (after we receive your distress call).
However, not in any contrived mental exercise, nor with different punctuation, can I make the exact sentence in the question remotely possible:
✘ We will be pending for her return.
Things can be pending, but things can't be pending for something. (Unless it is a period of time, but that's specifically different: Approval will be pending for hours.)
So, although I can come up with meaningful variations of the original sentence, some of them more contrived than others, I can't make it work exactly as it's written.
Even if I could figure out a convoluted mental exercise whereby those exact words could be used, it would be so unidiomatic as to serve no useful practical purpose.
For the sake of completeness, here is Merriam-Webster's definition of pending:
1 : DURING
// their opportunity to develop trade pending the laborious and fruitless negotiations
— Theodore Hsi-En Chen
2 : while awaiting
// pending approval
// were held in custody pending trial
1 : not yet decided : being in continuance
// the case is still pending
2 : IMMINENT, IMPENDING