her relationship with her boyfriend is not the question here. she did not ask for judgements on the quality of her relationship - it is no-ones business.
i don't think you can retrieve the messages, so i would advise not deleting them until you are sure it is not something more sinister, and just a daft joke.
also they may be intended for someone else so if they don't actually say your name, they could be for the person who had the number nefore you.
also text them saying your name -a fake one - and they may stop if they think they are going to a stranger.
also just ignore them - the more you respond, the more they will.
it happened to me once when i texted an old mate who had since chyanged his number - the new owner was a disgusting weirdo who seemed to delight in pretending to be my mate and trying to upset his friends... god knows how much trouble he caused with people who did not sus out that it was not my mate responding!
someone once told me that they took their phone to the police and a pc phoned the number from the station and warned the person off, saying to call him back or check out the number if they didn't believe he was copper - it worked. could be worth a try