How would I say this sentence correctly? [closed]

I am not quite sure as to the need for highlighting the fact that she has been looking for job for 6 months.

How about :-

Macy's responded to her online job application inviting her for an interview.

However, if you do need to highlight the 6 month search, then one option i can think of might be :-

Her 6 month job search has culminated in Macy's inviting her for an interview in response to her online application

I suggest you drop 'from a job application' as it is pretty much implied.

After six months of looking for a job, she finally got a reply from Macy's asking her to come for an interview.

You can start by using the correct article "an" when referring to "interview."

You would be better to use "through" than "from" here:

After six months of looking for jobs, she got a reply through a job application she posted online from Macy's asking her to come to a interview.

Better still:

After six months of looking for jobs, she got a reply from Macy's (through an application she had posted online) asking her to come to a interview.