Spoilers: I'm going to stick to Basics for a while, even though they contain spoilers...
Age: undecided - maybe ~160, maybe ~250
Looks: buxom, short, long dark green hair
Character: Normally sweet, but she can turn drill sergeant instantly.
Special skills: Solid military healer and non-com.
Family: Adopted daughter of Günter von Krist - we've never seen that story. Married Murata Ken during PW. Missed several stories in the series, living in Tokyo while Murata finished a university degree. As of Epilogue, they're back in Shin Makoku. Without consulting his wife, Murata adopted a baby centaur, Lucy, during GoT, and committed to stay in Trondheim, to complete what he began with the ghost of Franklin von Trondheim. We can imagine he got an earful for this, especially if Giesela shares her father's Krist racism against Tronds (very likely).
Don't have any illustrations of Giesela yet, but I'd love one in her misbegotten brides-maid dress for Wolfram's wedding, especially with Flurin looking lovely in her copy of it. ;)