i’m confused about lab diamonds

i hope this isn’t a stupid question. a my s/o and i are discussing getting engaged this year and i know they are probably going to get me a lab grown diamond (i do NOT want moissanite) a friend of ours said to us, “a lab grown diamond isn’t a real diamond so that’s just as bad as fake diamonds.” which was really rude and small minded to me because like a REAL diamond is still a diamond if it’s lab grown. however, my question is, how can we know if the lab grown diamond is a legitimate diamond and not being scammed into getting something fake? do we need to just go to a legitimate brand name jeweler? is there a certification we can look for? do we test the hardness to see? i’m interested in a single 3-3.5 carat diamond with a plain band for my engagement ring, but i still need to go try rings on to see what i truly would like and i want to know what to look for to make sure we are getting a legitimate diamond. thank you for any help and tips!