Acceptable or No?

[Flaming_Redhead]

Firstly a sub does not belong in a M/s relationship.

Umm...firstly, while all subs are not slaves, all slaves are subs.

The mindset of a sub is different than that of a slave.

I don't disagree with you there, but it's possible for a sub to become a slave over time or with the right person.

Those who enter into an M/s relationship usually do so after much discussion of hard and soft limits, setting boundaries, building trust and respect.

Again, I'm not going to argue with that.

There should be no safe words in a M/s relationship, they are for D/s relationships.

Says who? They may not ever need them, but everyone has a right to utilize them in their dynamic if they choose to. For instance, the Master may purchase a new whip and tell the slave to say a certain word if it really hurts so he can gauge the effect the whip is having.

The slave becomes the property of the Master, to be used or discarded as the Master sees fit.

Right.

The slave is entirely dependant upon the Master and it is a function of that role to look after the well being of the slave.

The slave is only dependant if the Master wishes it. Some prefer their slave to bring in an income.

The scenario put forth here does not work for it mixes dynamics from two different lifestyles, two different mindsets.
A sub can safeword and a Dom sould respect that, not so with a Master and slave..

I kind of thought the same thing when I first read the scenario. It looked to me like a sub got in over her head and didn't really understand what she'd signed up for, and then, she tried to get out of it by using a safe word. However, again, it depends on the contract. If this was, indeed, a no holds barred/no limits relationship, I don't know that a safe word would exist. However, if the slave had negotiated the use of a safe word prior to accepting the collar, and unless the Master stipulated that it couldn't be used during punishment or that he could assess the situation and choose to ignore it, I think he should've stopped to see what was the matter.