It's hard to look at her work as anything but criminal when she used 20 fake identities to pull this off. Once she ran out what she could do under her own name and started using fake ones, she crossed a line.
How do you know this? This may be a pre-emptive strategy
Also, as mentioned in other comments: She didn't use fake identities, she booked on the behalf of family and friends.
Edit: Reading your comment again, maybe my statement was already implied.
Edit: The article details that part of the strategy employed was to attempt to get a refund for any flight that ended up not being delayed, which would probably qualify as fraudulent intent (I think? IANAL).
Free Advice: if you run afoul of the tax system, pay first and challenge later. You're likley to lose and the punative penalties can bury you.
Perhaps we should talk about what actually happened - this woman defrauding companies using fake identities - and not hypotheticals we're making up.
Both are equally illegal in most parts of the world. Intentionally muddying your identity to defeat mechanisms put in place to avoid abuse is fraud.
Contrary to what some people on HN seem to believe, most legal systems in the world don't look too kindly on people intentionally abusing contracts. If it can be shown you signed a contract knowing that your understanding of it differed from that of the other party with the goal of exploiting this difference of understanding, which is to say in bad faith, you are very likely to lose in court.