They didn't steal or infringe on her trademark AT ALL.
If that were the case, TV directors and authors would be sued left right and center for using words like "Tesla" or "Coca Cola" in their writing.
Here is an extract from a website explaining trademarks:
A trademark does not mean that no one else can use your word, phrase, or symbol in connection with any and all goods and services. It means only that somebody else can’t use a similar trademark with
similar goods or services. The key criterion: trademark infringement occurs when someone else’s use of a trademark would likely cause confusion about the source of goods or services.
(see full article here:
https://slate.com/news-and-politics/2002/02/can-you-trademark-the-phrase-let-s-roll.html)
You cannot trademark a phrase, and when you do trademark something, you have to be specific with what you're trademarking. For example, An Australian car repair shop decides to open a shop and call it "Fleur de Force" - Fleur would have ZERO legal legs to stand on. Why? Because her name isn't trademarked against car repair shops and it in no way relates to her brand and no one would get confused by the car repair shop in Australia and her YouTube channel.
In the same way, authors are protected from writing a book about a character who loves Walkers crisps and it may even be entitled "I love Walkers Crisps" - Walkers Crisps could not sue that author for infringement because they did not infringe on their copyright in any way. Walkers will have trademarked their name for FOOD PRODUCTS, not for anything else (very likely). As I said, you have to specify what you're trademarking the name of something FOR - it cannot be a blanket trademark.
In this case - they just used the term as a pun. It's not the name of the magazine, and they're not selling it under that name.They could have put "Barbie girl" on the front cover instead and, again, Barbie's trademark would not be infringed upon