Is the phrase "She is not working now, because she can’t find an interesting job." OK? To me it sounds like the author should have used Present Simple instead of Present Continuous because they are talking about a rather prolonged activity with no end or beginning specified. To me this sentence sounds like "She is not working at this exact moment, she is taking a small break an will return to work soon", not like "She spends days and days without a job".
If by "present simple" you mean,
She doesn't work now because she can't find an interesting job
you have a point. It makes sense to use the present simple for a general or repeating situation.
Nevertheless, in this context, is not working is completely natural. It implies the situation is temporary or likely to change at any time. I can't say for certain, but it's possible this is because working is also a participle that acts like an adjective, and which (depending on context) means either "part of the workforce" or "proletarian". Example:
My father was a simple working man, who never really learned how to invest money.
So, in your example, "is not working" is taken to mean "she is not currently part of the workforce", with the nuance that this could change any time.
Other examples of this:
She isn't playing professional tennis these days, not since she broke her wrist.
He is waiting tables to make ends meet while he looks for his next acting gig.
Again, in both of these it would be fine to use the present simple, although this might imply a more permanent situation:
She doesn't play professional tennis these days, not since she broke her wrist.
He waits tables to make ends meet while he looks for his next acting gig.