An association may be made at credit reference agencies between you and your boyfriend if you apply for credit together, and possibly a link made with your mother as you are her daughter.
It does depend on each agency. Write / phone experian and equifax and get a copy of hte report.
If your mother finds she is linked with your boyfriend, she can file a "Notice of Disassociation" to get the link removed.
Hope this helps.
I think the websites are www.experian.co.uk and www.equifax.co.uk