Fu Lyanna was still fundamentally a mage type contestant.
That determined her weaker life force. When facing physical long-range shooters or close blade-type combatants, the Metals Professor could still wrap herself with a metallic shield to reduce physical damages. In that manner, she could trade damage for damage, which normally resulted in her having the last laugh.
Her damage reduction ability was a little similar to Sheyan's innate 'Stronghold'. Firstly, it enhanced defense substantially and even reduced incoming damage, but of course, its precedence rate couldn't be compared to 'Stronghold' and was only effective against physical damages. Without a doubt, a physical damage dealer would be in for a headache upon encountering her.
However, Zi's attack was based on force damage! It was equivalent to a form of element attack, which rendered the Metals Professor's metallic shield utterly useless.