She is not sure whether she cut her hair properly in order to exit from ihraam for Hajj. What should she do?

The scholars have stated that if a person does an act of
worship and finishes it, then is uncertain as to whether he has completed it
or not, and this doubt does not reach the level of certainty, then no
attention should be paid to it and the act of worship is valid and complete,
in sha Allaah. 

This applies especially in the case of one who experiences a
lot of doubts concerning acts of worship. It is not permissible for such a
person to pay attention to his doubts, for they are tricks of the shaytaan. 

Ibn Qudaamah said in al-Mughni (3/187): 

If a person has doubts
about his tahaarah (purity) whilst he is doing tawaaf, that tawaaf is not
valid, because he had doubts about a condition of worship before he had
finished it. The same applies if he has doubts about his tahaarah whilst
praying. 

But if the doubts come after he has finished the act of
worship, then he does not have to do anything, because a doubt about an act
of worship after it has been completed does not have any effect on it. End
quote. 

Al-Zarkashi said in al-Manthoor fi’l-Qawaa’id al-Fiqhiyyah
(2/257): 

Imam al-Shaafa’i
differentiated between doubts during an action and doubts after an action.
In the second case he did not say that it must be repeated, because that
would cause hardship. If a worshipper were required to remember what he had
done in prayer, that would be too difficult for him and no one would be able
to do that, so there is some leniency in the matter. End quote. 

The Standing Committee was asked the following question:  

Should any attention be paid to doubts about the number of
rak’ahs, or the number of circuits of tawaaf or saa’i, after the action has
been completed? Is that also the case with regard to wudoo’ or not? i.e.,
should no attention be paid to doubts that come after the act of worship has
been completed? 

They replied: 

No attention should be paid to doubts that come after
completing tawaaf, saa’i and prayer, because it seems that the act of
worship is sound. End quote. 

Fataawa al-Lajnah al-Daa’imah,
7/143 

Shaykh Ibn ‘Uthaymeen was asked about a person who
experienced a great deal of doubt concerning his prayer: what is your
advice? 

He replied: 

No attention should be paid to many doubts, because that will
lead to waswaas (whispers from the shaytaan). The shaytaan will not stop at
raising doubts concerning that, rather he will make him doubt other things,
until he even makes him have doubts concerning Tawheed and the attributes of
Allaah, may He be exalted, or he may make him wonder whether his wife is
divorced from him or is still his wife. This poses a threat to a man’s
sanity and his religious commitment. 

Hence the scholars said that no attention should be paid to
doubts in three cases: 

1 – When it is simply imagination with no basis in reality.
This should be ignored completely and no attention paid to it at all.

2 – When there are many doubts and a person has doubts every
time he does wudoo’, or every time he prays, or every time he does
something. This should also be ignored completely and no attention paid to
it at all.

3 – If the doubt comes after completing an act of worship. No
attention should be paid to it so long as one is not certain of the matter. 

For example: if a person
is uncertain, after saying the salaam at the end of the prayer, whether he
prayed three or four rak’ahs of a four-rak’ah prayer, he should not pay any
attention to this doubt because he has completed the prayer. But if he is
certain that he did not pray more than three rak’ahs, he should do the
fourth rak’ah if he has just recently completed the prayer, then do the
prostration of forgetfulness after saying the tasleem. If some time has
passed, then he should do the whole prayer over again. End quote.   

Majmoo’ Fataawa Ibn ‘Uthaymeen, 14/
question no. 746 

And Allaah knows
best.