かもしれない is one of those things that’s often taught as if it’s a whole word to be memorized, but it’s actually a few parts that are often packaged together.
The か, as mentioned above, acts like a question mark on the preceding clause.
The particle も is the inclusive topic particle. It’s like the exclusive topic particle は, except it’s inclusive rather than exclusive.
As an example of the two:
「キリンの首は長い」 “A giraffe’s neck is long.” (Unlike those other animals’ necks, a giraffe’s neck exclusively is long.)
Here, the topic is “giraffe’s neck”, and we’re making a comment that cannot be said about whatever topics we were previously talking about. If the prior topic was a tiger’s neck, the comment “it is long” would be wrong. Between the prior topic (tiger’s neck) and current topic (giraffe’s neck), the comment “it is long” is exclusive to the giraffe’s neck.
「フラミンゴの首も長い」 “A flamingo’s neck is also long.” (Just like another animal’s neck is long, a flamingo’s neck inclusively is long.)
Here, the topic is “flamingo’s neck”, and we’re making a comment that can be said about our prior topic of the giraffe’s neck. Between the prior topic (giraffe’s neck) and current topic (flamingo’s neck), the comment “it is long” is inclusive to both the flamingo’s neck and the giraffe’s neck.
At this point, we have:
The phrase is a question (か), and we’re marking it as an inclusive topic. That means the following comment will be something that applies to other topics. (Note that it doesn’t have to be a topic that was just talked about as per my animal neck examples above.)
The comment is:
This is the verb 知る (“to know”), but it is in the potential form 知れる (“can be known”) plus ない to make it negative (“cannot be known”).
“The (answer to the question) [phrase] also cannot be known.”
There are all kinds of topics of which the comment “cannot be known” can be said, and this question is also one of those topics.
Translation: " ‘Is it that she is throwing away her life?’ also cannot be known."
Consider the following English sentences:
- It can’t be known (right now) if I can win a marathon.
- It can’t be known (right now) if I can learn 2,000 kanji.
- It can’t be known (right now) if I can read this manga.
- It can’t be known (right now) if my pet cat will lock me out of the house again.
In these sentences, we’re essentially pondering whether something is the case or not. “Can I learn 2,000 kanji? Well, I can’t know that right now.”
Translation: “Is she throwing away her life? I can’t know this (right now).” He’s pondering on whether she’s throwing away her life.
Many resources will tell you that かもしれない means “might”, but really there’s so much more to it!
(This is one of those topics that I’m still not good at explaining, so I apologize if it’s a bad explanation…)
Side-note: I’ve only included the last part of the line from the manga panel here, so the translation is on only part of the whole sentence.