So on all of my builds I always buy barrel and bolt together since most companies check the headspace for you, or so I think? anyway I helped a friend with a build using BCM barrel and bolt carrier, well she ordered the barrel and bolt at separate times so Bravocompany couldn't have headspaced them together. my question is, with the quality of the parts should I check headspace or no?

You should always check it when you install a barrel.

On a used barrel....always.
On a factory new barrel from a reputable manufacturer....not as necessary.
95% of the time you can drop a QUALITY bolt and barrel together without any issues...with that being said, factory duds have been known to make it past quality control so the question is do you want to gamble with that 5%?

I am in that 5%.  High quality barrel and BCG from different manufacturers.  Good reason to check because they are two different manufacturers.  Barrel was in spec, the bolt was out of spec.  Both companies have great customer service and the issue was remedied.  The bolt was something that slipped through the QC process and I suspect being as good a company as they are, they tightened that up.  I would have not expected to have any issues, but I'm glad I checked.  $60 for headspace gauges $15 for a bolt vise and 10 minutes to do the check.  Well worth it.  Check your headspace.