She's a limited seasonal with poor IV's. Any primo skills like Bold Fighter or close counter are much better used on a unit that will be merged so that you can make use of them in arena.
DD9 is pretty crazy. My Zephiel can tank a fully buffed Reinhardt with DD9. He can do it with DD6 as well but only because of wary fighter or if he gets to KO on retaliation with DC.
Pokemon GO
Fire Emblem Heroes
Fate Grand Order
Dragonball Legends
Dragalia Lost
IV Calc
Heroes