Which Shakespearean sonnet would fit the relationship of Helena and Demetrius from A Midsummer Night's Dream?

One Shakespearean sonnet that would fit the relationship between Helena, the unnoticed, and Demetrius, the betrothed (yet unwanted), is Sonnet 80. It is part of what is referred to as the rival poet sonnets that extend from 79 through 86. With some fancy substitution of a pronoun here and there, the sonnet gives a fairly good picture of Helena's feelings regarding her situation with Demitrius.

Helena is Hermia's dear friend. Helena loves Demetrius. Hermia loves Lysander. No problem there. However, Hermia's fatehr has insisted on a betrothal between Hermia and Demetrius--yes, Demetrius. To further complicate things, Demetrius is glad because he loves Hermia. This means of course that since he loves Hermia he can't possibly love Helena--and--Helena loves Demetrius.

The speaker in Sonnet 80 laments in a conceit calling forth weakness, which transitions to an ocean and drowning conceit, that the beloved one is praising the virtues of someone else. There is a comparison of the physical qualities of each followed by the possibility of an ocean wreck in which the speaker will be cast away, with love the decay.

If I may be allowed to take liberties with Shakespeare's beautiful sonnet, Sonnet 80 may be amended for Helena as the speaker as follows:

O! how I faint when I of you do write,
Knowing a better spirit doth use your name,
And in her praise thereof spends all your might,
To make me tongue-tied speaking of her fame.
But since your worth, wide as the ocean is,
The humble as the proudest sail doth bear,
My saucy bark, inferior far to hers,
On your broad main doth wilfully appear.
Your shallowest help will hold me up afloat,
Whilst she upon your soundless deep doth ride;
Or, being wrack'd, I am a worthless boat,
She of tall building, and of goodly pride:
Then if she thrive and I be cast away,
The worst was this, my love was my decay.

Here is Shakespeare's original, untampered with, Sonnet 80:

O! how I faint when I of you do write,
Knowing a better spirit doth use your name,
And in the praise thereof spends all his might,
To make me tongue-tied speaking of your fame.
But since your worth, wide as the ocean is,
The humble as the proudest sail doth bear,
My saucy bark, inferior far to his,
On your broad main doth wilfully appear.
Your shallowest help will hold me up afloat,
Whilst he upon your soundless deep doth ride;
Or, being wrack'd, I am a worthless boat,
He of tall building, and of goodly pride:
Then if he thrive and I be cast away,
The worst was this, my love was my decay.