Her menses started after the time for Zuhr began; should she make it up when her period is over?

Firstly: if the period
comes after the time for a prayer has begun, when enough time has elapsed to
pray one rak’ah, then you have to make it up when you become pure (i.e.,
when the period ends). Shaykh Muhammad ibn Saalih al-‘Uthaymeen (may Allaah
have mercy on him) was asked about a woman who got her menses when enough
time to pray one rak’ah had passed: does she have to make up that prayer?  

He replied: If a woman’s
menses comes after the time for prayer begins, then when she becomes pure
she must make up that prayer during the time of which her menses came, if
she did not pray before her menses began. That is because the Prophet
(peace and blessings of Allaah be upon him) said: “The one who catches up
with one rak’ah of the prayer has caught up with the prayer.” If enough time
to pray one rak’ah elapses then the woman’s menses begins before she prays,
then when she becomes pure she has to make it up. End quote. 

The time for making up the
prayer is as soon as the excuse no longer applies. So when you become pure
following menses, you must do ghusl and offer the prayer that was due, even
if it is not the time for that prayer, and you should not wait until its
time on the following day, because the Prophet (peace and blessings of
Allaah be upon him) said: “If a person forgets a prayer, let him offer it as
soon as he remembers; there is no expiation for it other than that.”
Narrated by al-Bukhaari (597) and Muslim (684). 

Secondly:

If a woman becomes pure
before the time for prayer ends, then she must offer that prayer and the one
that may be joined to it, according to the majority of scholars. 

For example: if a woman
becomes pure before the sun sets, she must offer Zuhr and Asr together. It
says in Fataawa al-Lajnah al-Daa’imah (6/161): If a woman becomes
pure from menses or nifaas before the time for an obligatory prayer ends,
she must offer that prayer and the one that may be joined to it before it.
If she becomes pure before the sun sets she must pray ‘Asr and Zuhr. If she
becomes pure before the second dawn breaks, she must pray ‘Isha’ and
Maghrib. If she becomes pure before the sun rises she must pray Fajr. End
quote. 

We have discussed the
difference of opinion among the scholars concerning this in question no.
82106. 

And Allaah knows best.