Hey Gemma,
Love Eliza’s tips- would definitely agree with all the above! I would also get her to speak the lyrics (without singing) in her own accent (whatever that may be) and then sing straight away keeping the accent exactly the same as when she spoke the lines aloud. Even doing just a few lines at a time- she will start to recognise how she naturally pronounces words. Taking on an accent can be due to listening to so much i.e. American singing – but also being insecure in using own voice- feeling it’s not good enough for example so I would be ultra encouraging when she does achieve a natural accent and make her feel comfortable with her own accent! Hope this helps x