I believe that this poem is a lament for what could have been but is not. The poet states that she never feels alone because her dreams often transport her to a different world.
The poet first "dreams" that she is a mother, cuddling, comforting and loving a child.
Then I may cherish at my breast
An infant's form beloved and fair,
May smile and soothe it into rest
With all a Mother's fondest care
Then she dreams that she is loved by someone.
To feel my hand so kindly prest,
To know myself beloved at last,
To think my heart has found a rest,
My life of solitude is past!
She ends by asking God why he has given her a heart with such an immense capability to love if she is to remain alone, only dreaming about being loved and having a child to love.