Is relieving letter important?

[snvlkumar]

I am getting married in a month. My fiance is currently in India and her company has a 90 day notice period which we are not ready to wait. Hence the company is not willing to provide a relieving letter.

her back ground:

First employment 4 years: All documents available:

Second employment (current): 2 years; she wont get relieving letter.

Now the question is,

how important is relieving letter?

a) if she applies for a a H1 B at a later a point; will this bother her job employment prospect?

b) If I get a GC and if she looks for a job will she be able to use this second two year experience without relieving letter?