Is a voluntary fast valid after performing ghusl due to doubt about penetration?

If the husband fondles his fasting wife, and he penetrates or she experiences an emission of manī, her fast is invalidated if she is certain of that or if she predominantly believes so. Otherwise, her fast is valid. If a voluntary fast is intentionally broken, one is not obligated to abstain for the rest of the day. Scholars differ regarding the obligation of making up the fast (qaḍāʾ). The majority view that it is not obligatory, citing the hadith: "The one observing a voluntary fast is the master of himself." However, the Hanafis and Malikis believe that qaḍāʾ is obligatory. The preponderant opinion is that qaḍāʾ is not obligatory. A woman should not observe a voluntary fast while her husband is present except with his permission, and she must respond to her husband if he calls her to bed.