Depends on the build, really. Firesweep/Desperation builds don't necessarily have to worry too much about the defense (as long as it's not too low) and, again, depending on the build, she won't really be doubled except by the speediest of unit
Though -HP would be ideal, I feel like with -Def she still does her job as a brave lance user with DB and Def Ploy. I don't think it makes such a big difference, so I'd say go for it.
BTW, she can work with Ridersbane and Slaying spear as a dedicated OHKO killer too.
Wait, isnt Est considered to be the best of the whitewings? And also, she used to be the best available in the 4 star pool, unlike cordelia and Clair lol, but a good old fashion Brave lance set wouldnt hurt, or a slaying spear set
Est, in my opinion, is probably the bEst of the Whitewings (pun intended, shoot me). After her, I'd probably say Catria is second, then... Palla... Yeah.
My friend said she’s trash, but I didn’t know. I don’t really use fliers. I do plan on making her offensive with a brave lance set since her speed and defense are both meh.
My +Atk/-Def Est, I like using her in my flier teams. The -def hasn't seemed too detrimental since with this set she really wants to just KO and be repositioned back to safety.
If you are going to use her with Brave Lance and Death Blow, that's the ideal IVs. If you want to invest her with a powerful set, you can run something like mine's, which is +res -spe:
Pokemon GO
Fire Emblem Heroes
Fate Grand Order
Dragonball Legends
Dragalia Lost
IV Calc
Heroes