My wife's contributions are not acknowledged in our group's paper that has me as coauthor. Should I speak up for her?
I think you should talk to the group leader about the appropriateness of an acknowledgment  for the drawing (not coauthorship).
This is the right course of action for any contributor. The fact that she's your wife is not relevant, and should not be a part of this professional conversation.
How to approach the group leader depends on how you usually interact. I think a short conversation is probably appropriate. You could follow up with an email for the record if that seems appropriate.
Of course the group leader probably knows about your relationship, but that should not affect the decision.