Hi,
The transfer of assets between spouses and civil partners are not taxable. If you transfer the crypto to your civil partner, there is no captial gains liability on the transfer.
Your partner will acquired the crypto at the value you acquired it for, so that when she sells the crypto, the difference between the disposal value and the acquisition value is either a gain / loss.
The gain would be taxable and would be reported using the realtime transaction service at:
Self Assessment tax returns
Losses would need to be claimed either in a self assessment tax return or in writing.
Thank you.