Welcome to the Wefugees Community and thank you for reaching out to us.
I am afraid that "cancelling the asylum" in Italy and then apply for asylum in Germany is not really working. German authorities will find out that she applied for asylum in Italy already and ask her, according to the so-called Dublin regulations, to go back to Italy. Of course, if you are able and willing to marry, things will be much easier. If you, as Spanish citizen, enjoy the so-called freedom of movement (EU law) as, for instance, employee in Germany, your spouse will also be allowed to stay with you in Germany (also being allowed to work, receive social benefits etc.).
I will also link two of our experts here. Dear @mbeon-fardeen and @mbeon-Rukundo, am I right on this and/or can you add further information?
I hope this helps and please don't hesitate to get back to us with any further questions.
All the best,