I will sincerely recommend your friend to get a lawyer specializing in German immigration law. It seems indisputable that your friend, albeit for a short period of 10 days, stayed illegaly in Germany and if the immigration officer found it serious enough to initiate a criminal process, the outcome is not unlikely an entry ban.
Being a tourist is probably not a good excuse for not knowing that you have to somehow deal with an expiring visa if you are prevented from leaving the country. Being infected with covid is also not necessarily preventing anyone from doing so. Your friend could have contacted the authorities both by e-mail and phone. In this situation, it should have been absolutely no problem for your friend to get a visa extension.
If an entry ban is imposed, it will be for the entire Schengen area and prevent issuance of a regular visitor visa. Dependent visas will not be categorically refused even if an entry ban is in effect, but the circumstances of each case will be evaluated.
Credit:stackoverflow.com‘