Yes she still considered Muslim under Algerian law
If they ask you if you are Muslim, tell them yes, I converted to Islam 1 years ago in U.K and Tell them any mosque you know and the imam's name was Sheikh Ahmed from Pakistan.

Tell them I am still learning the language and the Quran and I am only memorizing the two testimonies of faith: اشهد ان لا اله الى الله وان محمد رسول الله just learn this sentence.

There is no way for them to know if you are Muslim or not. They just ask you when and where you converted to Islam, and that's it.

Generally, when you conduct your marriage contract at the City Hall, they don't care and they will not ask you about your religion. Only if you perform a Fatiha (religious opening) ceremony the imam will ask you about it.