Murmuring how she loved me — she
Too weak, for all her heart's endeavour,
To set its struggling passion free
From pride, and vainer ties dissever,
And give herself to me for ever.”
The speaker is aware of Porphyria’s passion and desire for him
The speaker’s emotions begin to get the better of him as he begins to consider her weaknesses (her lack of commitment to him) which he sees as vain
This presents his jealousy as stronger than his love for her