The term "heritage", while rich in respect to the history of a breed, must also include the necessity of being bred to meet the APA accepted Standard for the breed. This is important to remember, otherwise, the term "heritage" gets abused in far too many cases as merely a promotional or marketing gimmick.
OK, with that being said,
A true bred RI Red is one not only because of deep color. The bird first and foremost most have the brick body shape of the breed. It is not easy to tell from the photos as to the body shape of your bird.
The tail is quite pinched, as you yourself noticed. Unless you're are going to breed her, using a Standard bred male, none of this is really important. If she's going to live out her life as a flock member in your backyard, her lack of conformation to the Standard isn't really all that important. If you don't intend to exhibit her, then again, her lack of conformation is of limited importance to you.
Finally, some lines or strains of exhibition lines and Standard bred RI Reds do indeed lay earlier than other lines. One really cannot make over generalized statements that apply to all lines.
If she's a good flock member, happy and healthy, then you're gonna be pleased with her, I am sure.
