What are the possible reason visa will be delayed or refused?

Hi

I am Sri Lankan origin and australia citizen.
I been travelling india every year without any problems
sometime with my mother also.

This my mother visa was " still under assessment by consulate"
even when went to consulate and met one officer..he refused to give reason
and say it may take several months..but we wanted go for important family wedding this Jan 19th.

she got visa on 2010 within weeks...only different she did this time ( my mother)
went to canada for sometime...and returned.

what are possible reason visa can be delayed?
it would be useful to know...that we can provide right documents?

My mother was hospitalised in Canada for one day for not feeling well? Even though she paid the bill, hospital missed some bill and that has not been paid
would that affect indian visa?

I have asked the hospital clear that record if there is any..as all balance has been paid now.

what is the next best approach in terms of getting visa
Who can be approach?

I love india that is why Travel yearly...but visa system is very disappointing...

any helpful thoughts pls