Show me where in the UCMJ it prohibits soldiers from civil lawsuits?
Article 92, UCMJ.
Uhm, read the complaint. The UCMJ code that the plaintiff seeks to have declared unconstitutional says that — which is why she’s seeking to have it declared unconstitutional.
Nowhere. She's within her rights to file any suit she wants. But she's expected to obey orders in the interim. If she refuses to go then she can be charged with any number of violations of the UCMJ.