VHI will cover a maximum of 180 days in-patient/daycase treatment per calendar year, as per Rule 6(d) on page 5 of
their rulebook for Plans A to E. It's the same for the other VHI products, as this is the minimum laid down by Regulations.
Something else your relative may need to consider is that any treatment he/she had this year, prior to this admission, is also included in the 180 day max.
As John M says, the best thing to do is have the relative ring VHI to discuss. Also have a word with the hospital staff to see what alternatives can be put in place, e.g. if it's a public hospital, can the relative be transferred to a public ward instead?
Also, additional cover isn't available by switching to another insurer. Once a member reaches the 180 day max, you don't get anything extra until the new year starts.
Sorry I don't have any good news, but I hope it helps and that your relative gets well.