Installation in Subdomain of Main Site vs Main Site

Hi,

New to WP, but I understand the basics and overall concept.

My client’s website is “abc.com” (main site). She owns another domain “def.com” that will be her blog. My thoughts were the following:

1. place a directory named “def” into the “abc” directory (as a subdomain, right?)

2. import the entire “abc” site into WP (thereby including the “def” subdomain or must I deal with that separately?)

Questions

1. Is this the most common/best way to do it?
2. If I do this, can I show “recent posts” (or excerpts), etc. on a “blog page” in the “abc” site as kind of a “preview” or “teaser”, and then allow them to go to the “def” main blog site?

I wrote the question this way to keep my babbling to a minimum and help my new friends to help me more efficiently. Do ya’ll mind answering “in kind”? No demands, at all. This would be so much easier, I think.

Thanks so much, guys and gals!!!