Crypto Tax

By default, any income worldwide is taxable in Germany while you reside here - this is true for crypto gains as well as all other sources. She will have to include any realised gains in the tax declaration next year.
Many countries have tax treaties with Germany that in some cases (but not all!) prevent double taxation. If a treaty exists with your country and it gives your country the right to tax such gains, they are not taxable in Germany. But you still have to declare them, because the tax authority (not you) decides what is taxable and what not. (Not declaring is a criminal offence and can get you into more trouble than it's worth!)
Engage a tax consultant to do all this right!

Just for completeness sake: There is also a gift tax for presents to others (up to 50% of the gift is due as tax!), but the tax-exempted amount for married couples is € 500 000 within 10 years, so hopefully that will apply to you. (If you are not legally married, the exempted amount is far lower.)