Sitting is fine! She can't point her toes, but she doesn't fall over backwards like most strung dolls do. The elastic crossing in the pelvis really makes a difference in how well these dolls sit. She can cross her legs with the mobility thigh:
That's the best she can do to lean forward. She can hold her legs up unsupported, though!
Everyone else here needs wire to do that successfully. She can stand with her legs apart, but not too far, and she tends to snap her legs back together if she is bumped:
And while she has double jointed knees, they get weird when she does the "schoolgirl sit" (To be fair I couldn't do that even if you paid me, I would have the same problem with my knees:)