What else can I do? AKA. The child is a Lich! Situation

[Astralia123]

I'm slightly confused with the language but...okay.

From what I have seen, some DMs tend to set a really simple (to their own views) and once-for-all answer to such a dilemma. It is sometimes because they would award wits, and because they can then laugh at the foolish PCs who miss the most apparent hints.

On the other hand, some DMs tend to set very high prices for "playing noble", perhaps because "only willing sacrifice makes up good" sort of ideologies. Which could be your case, too.

I'm not sure which type is your DM, but if he is more of the latter type, then killing the lady and raise her later with a personal cost of you could be the intended solution.

But if he is more of the former type...Have you tried to make this lady a member of your ultra-powerful guild? Or have you exploited something of the spell, that can disable it by some other ways? For example, sending the lady to another plane, or making her "dead" by petrifying her or by spells like Temporal Stasis, or anything that could "exclude" her from the spell?
Or you can try to disable the bad guy's AMF casting ability, which is likely to be one of the possible solutions.