The german constitution restricts drafting to men[0] and would have to be changed before such a law could even be considered.
Before you ask, yes, the constitution also says that men and women need to be treated equally[1]
Just to add, the current government does not have the necessary majority to make such a change. Therefore making a law which includes drafting women is legally impossible without opposition collaboration.
Is there anything in the constitution that forbids the government from requiring citizens to perform some kind of service to the government?