what she said was true as far as it went - she was ushered out (that doesn't necessarily mean "thrown out"). She just completely misunderstood the reason. The Guardian's first sentence overcooks it - it says she was turned away because women weren't allowed; but when it actually quotes her, she says she just assumed this was the reason. In fact it wasn't; both Newman and the Guardian got it wrong.
The real reason was just that the people at the mosque hadn't heard about the open day, thought Newman was looking for a church, and tried to show her where it was. By the sound of it, the person who did this was just another worshipper who didn't necessarily speak good English.
Just a mixup, I think, and a professional reporter shouldn't have tweeted without finding out exactly what was going on. But tweeters do that all the time.