Not at all, I love a dialogue and welcome it,
My emphasis however is on which best suits ragini's character. In addition as you have rightly researched, ultamatum can be used for two reasons: as a final statement/ term, or a statement which is followed by a threat (note* this is done verbally) I didn't hear ragini follow the ultamatum with a threat.
But if you insist on the term 'to threaten', let just have a look at it's implications:
To threaten someone is to be of harm to them i.e. 'she threatened Sadhna', while to simply threaten is not necessarily to be of harm to anyone i.e. 'she threatened to leave the house' (her threat wasn't directed at someone). Therefore perhaps the conjunction of the action 'to threaten' with the subject 'Sadhna' is how you could have possibly given the implication that Ragini had cruel intentions.
I'm not saying the above was your intention at all, it's just simply my observation of your choice of words and why I agreed with s.sanj90 on that point. But your absolutely right... it is just my humble opinion at the end of the day.
Anyway, this is just an excuse for me to have a debate on an issue lol, perhaps this is the wrong platform 😆