What's the role of 一 in 听百灵鸟这么一说，她明白了?

Question

I know it's a grammatical role that 一 plays in such sentences, but unfortunately I didn't find it on Chinese Grammar Wiki. So what's the meaning of 一 in this sentence?

听百灵鸟这么一说，她明白了

I suspect it's "have just", but I want to understand it 100% correctly.

Answer 1

Talking skylarks?? Where are we??

I think you can understand this 一 as 'once' or 'as soon as'

听百灵鸟这么一说，她明白了。
As soon as she heard the skylark speak, she understood.
Once she heard the skylark speak, she understood.

You can also not translate it: Hearing the skylark speak thus, she understood.

Or, to borrow Tang Ho's example:

二人向来不睦，一见面就打架。
Those two are always at odds, as soon as they see each other, they start fighting.

Answer 2

[一 + v] = [once /upon + v]

听百灵鸟这么说，她明白了 = After hearing the lark said it like that, she understood

(一)听百灵鸟这么说，她明白了 = (Upon) hearing the lark said it like that, she understood

听百灵鸟这么(一)说，她明白了 = Hear the lark (once) said it like that, she understood

It would be easier to understand if we omit 听 and write: "百灵鸟这么一说，她明白了" = "The lark once said it like that, she understood" ("heard" is implied)

Note: depend on context [一 + v + 就...] can mean [once + verb + then...] or [would + verb + every time]

Example:

一見面就打架 = "Start fighting upon seeing each other" or "They fight every time upon seeing each other"

不知如何，這兩人一見面就打架 = For an unknown reason, the two started fighting upon seeing each other"

二人向來不睦，一見面就打架 = The two have not been friendly to each other, and they fight every time they meet"

Answer 3

This dictionary definition addresses the use of 一:

（用在动词或动量词前面， 表示先做某个动作， 下文说明动作结果）:

get over in one jump;

一跳跳了过去

This explanation of his restored our confidence.

经他这么一说， 大家又都有信心了。