@Iron Storm
I don’t think Rariety ever demonstrated her strengthnin episode one.In season 2 she carried a boulder she thought was a diamon on her back. She primarily uses her telekinesis as a seamstress.
Also note, this might be the heaviest thing Rarity not only picked up but threw with force. She generally is great with lots of small or midsized objects of limited weight. But a piece if masonry was her pushing her limits. That stone was bigger than Twilight is.