First of all, since the dominant is asking for peoples oppinions on the matte, I personally see no reason why they shouldn't be given.
To really respond however some questions about the situation require asking.
Is this a recent onset or long term online only or a real life relationship?
What degree of submission has the sub in question agreed to maintain ahead of time at this point in the relationship keeping the first question in mind (becuase some levels of submission simply are not possible depending upon the answer obviously).
More importantly, is this a standing command/ condition and or task that the submissive was made aware of prior to the "infraction" occuring?
It makes a hudge difference as to what kinds of punnishments are available and or to what degree of accountability and submission to one's dominion is possible or appropriate.
If it is recent real life arrangment I can't imagine why a simple spanking and or a few stern words wouldn't suffice, after all masterbaiting without permission is not exactly all that rare.
As for the lie in and of itself, as well as the infraction, such things can and do happen; and both are indeed as much a reflection of the dominant as they are of the sub.
D/s is after all a two way street.
Which means both the dom and sub have some work to do on the paticulars of the relationship.
If its a long term real life arrangment this type of thing should allready have been covered so I am guessing its not.
Was she "caught" or did she confess? Obviously a confession to the act should be wieghed in her favor.
Is this the first time or one of many occurances?
Additonally badkitty, you should be aware that no member can actually restrict another members access to the site, nor should they resort to such as a punnishment per say, especially if its an online only thing imho.
Eaither way you both have lots to think about.