Are there any notes written on the margin of the register? If so, it would likely indicate a reference to the Register of Corrected Entries (RCE) where additonal info can be included on the cause of a death following further investigation.
If there is an RCE, it has hopefully been linked to this image of her death index and should be able to be viewed by clicking on a button at the top of the page. It may however not be available to view online because it is not available or linked this way yet.
Monica