Thank you for reaching out to us and for contributing to our community with your question.
We have had a few similar questions already related to getting married in the UK, please have a look:
How to marry my British girlfriend in the UK?
Can a rejected asylum seeker in Austria marry a UK citizen and move to Britain?
The second thread I linked contains very detailed information on what steps you need to take in order to live together in the UK as a married couple.
If your girlfriend travels to Italy to get married, make sure that your marriage will be recognized by the UK in order to apply for a spouse visa after. All necessary information can be found here on the UK government website: https://www.gov.uk/uk-family-visa/partner-spouse
Here is a thread from our platform on how to get married in Italy:
Marrying an asylum seeker in Italy
Please note: In the UK, there is an option to apply for a "fiancé/ fiancée visa" that allows you to travel to the UK and stay for 6 months. In that time, you would have to get married. Once you two are married, you have to apply for an extension of your stay. Spouse visas allow you to stay 2.5 years.
I hope this information helps. Feel free to reach out to us again if you need any further assistance!
All the best,