Old @virginmedia email compromised, best way to resolve

Hi there, my girlfriend has recently had her old @virginmedia email either spoothed or compromised.

We have had a spam of attempted log ins on various services such as discord, in response to which we have moved all important and frequently used accounts to a new Gmail with new secure passwords.

However now it seems that emails are being sent from her account. When looking in the bin folder there are a series of spam/scam emails for various jobs offers being sent to random emails but using my girlfriends email address (with the owner name being changed).

We have tried to log into her virgin media account and change the password, but with this email address being so old it is not recognized on the virgin media website. And due to my girlfriend not having a virgin media membership for many years there has been very little help from the service desk(when we can actually get through to them)

Sorry for the wall of text, any advice would be really helpful as we are both slightly confused on how to proceed.