Change to passive: I understood that I could not rely upon her to get a job done.

I'm not sure... maybe, "I understand that she cannot get a job done."

in june, we will have been married for eighteen months. (i am assuming this is what you want? the sentence, as you have presented it, is grammatically incorrect--   you want it corrected, yes? )

i don't really know the circumstances. i personally think not due to it not being fair for all parties and how hated i'd become if i thought it was a good thing.