Agreed.
Of course you didn’t mean that she’s acting as a formal “defender of the bond”, but rather she may choose to use whatever influence she has as one of the two primary witnesses to the marriage to oppose the annulment. A witness can easily slant their very subjective evidence one way or the other (eg. emphasising that “due consideration” was either lacking or not). They also have the option of appealing the annulment after it has been granted (as pointed out above)
Her evidence will be considered along with any other presented to the tribunal (of course).
Why would a person who themselves later remarried oppose an annulment?
There could any many reasons. As someone has suggested earlier in the thread, it could be out of consideration for the children or it could be to control the situation. Perhaps they have reconsidered the whole marriage in a better light and see it has having been true?
It happened to me, albeit unsuccessfully. My ex-wife left the Church and also left me for another man (non-Christian), alleging that our marriage had been wrong from the start, and married him two years later. I applied for an annulment after five years, while she was still in her second marriage. She attended her interview and later told me that she went in with the intention of preserving the marriage! Knowing her as I do, I suspect this was partly out of spite, to keep me locked into a single life by my own religious beliefs, and also to maintain a “romantic” fiction about her own life and about her “first marriage”. (Her second marriage lasted ten years, before she “found real love” again).
At the end of my own interview the tribunal member asked me one last question “Do you expect your wife will tell the truth?”, anticipating that witnesses can lie to a tribunal, and that their testimony is important.
My annulment proceeded quite easily however, on grounds of “lack of due consideration” by both parties, and with other evidence.
