Her nifaas (postpartum bleeding) continued for nine months and she did not pray during that time

Firstly: 

We have previously discussed the difference of opinion among
the scholars concerning the maximum length of nifaas; the most correct view
is that it is forty days. See the answer to question no.
10488. 

Secondly:  

With regard to the bleeding that occurs after the period of
nifaas has ended, if it comes at the usual time of the menstrual period,
then it is menses and the woman should not pray or fast or have intercourse
with her husband at that time, until her monthly period has ended, as is
well known. 

If it occurs at a time other than the usual time of the
menstrual period, then it is istihaadah (non-menstrual bleeding) and in this
case she should fast and pray, and her husband may have intercourse with
her. But she has to do wudoo’ for each obligatory prayer after the time for
it begins, then with that wudoo’ she may offer whatever naafil prayers she
wishes. 

For more information please see the answer to question no.
106464 

Thirdly: 

The scholars (may Allah have mercy on them) differed
concerning the case of a woman suffering istihaadah if she refrains from
praying out of ignorance: does she have to make up the prayers that she
omitted? There are two opinions: 

1.    
That she has to make up the
prayers.

2.    
That she does not have to make
up the prayers. This is the view favoured by Shaykh al-Islam (may Allah have
mercy on him). 

Shaykh al-Islam Ibn Taymiyah (may Allah have mercy on him)
said: If the woman who is suffering istihaadah did not pray for some time
because she thought that it was not obligatory for her to pray, there are
two opinions as to whether it is obligatory for her to make up the prayers.
One opinion is that she does not have to make them up – as was narrated from
Maalik and others – because when the woman who was suffering from istihaadah
said to the Prophet (blessings and peace of Allah be upon him), “I have been
bleeding heavily for some time and it prevents me from praying and fasting,”
he told her what she should do in the future, and he did not tell her to
make up the prayers of the past. End quote from Majmoo‘ al-Fataawa,
21/102 

Shaykh Ibn ‘Uthaymeen (may Allah have mercy on him) said: It
is best if you pray what you omitted during the early days, but if you do
not do that there is nothing wrong with it, because the Prophet (blessings
and peace of Allah be upon him) told the woman who was suffering from
istihaadah and who said that she was suffering heavy bleeding during which
she did not pray to count her menses as six or seven days and to pray the
rest of the month, but he did not tell her to make up the prayers that she
had omitted. If she does make up the prayers that she missed, this is good,
because it may be that she was heedless in not asking, but if she does not
make them up there is no sin on her. End quote from Majmoo‘ Fataawa Ibn
‘Uthaymeen, 11/276 

To be on the safe side, your friend should make up the
prayers that she missed as much as she is able to. So every day she should
make up whatever she can of the prayers that she omitted during this time,
because it seems that there was a kind of heedlessness on her part as she
did not ask even though the time during which she did not pray was lengthy,
and usually one does not stop praying for so long. Moreover, she used to
pray sometimes, which indicates that perhaps she knew that she should be
praying. See also the answer to question no.
31803. 

And Allah knows best.