The weapon requires at least 18 faith to use and has some faith scaling. If you already have any weapons that have fire damage or some fire grease it may help with Romina now. Mesmer is an interesting fight, and I think required so you'll have to back track eventually.
There's always stuff like fire grease then to give your attacks a bit more kick. I was curious so I looked it up, she can also be frostbitten and bled.
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