She came home! Build suggestions?

Sub 20 Orbs and:

+Atk -Def! Petra was always my favorite female in Three Houses (though Lysithea and Marianne made it hard to keep thinking that) and I remember giving up on her release banner because Hubert butted in as Foxtome fodder.

Any recommended builds or partners? I have an Athena that can activate her weapon’s effect, but I was also considering Astram as soon as I get more Bonus Doubler since he can help stack more skills.

I was considering Sturdy Impact since I have given it to all the units I care about getting it (I’m planning Mirror Impact on Cormag instead, I’m running DC Vantage on Keaton, and Velouria is better as a cleanup support) but should she run it despite the Def bane?