Sorry to hear about what has happened. She WILL get better and does need her second dose.
In Britain we use a heptavalent vaccine (yes, 7 agents in one), and give the vaccines into the loose skin at the side of the neck subcutaneously. I have had granulomas up to about 1cm in diameter, but never any abscesses. As part of the vaccine is live, skin antiseptics should not be used, but I clean up the needles in boiled water after every animal and thoroughly sterile the injecting equipment prior to use.
To get an abscess may be down to 'dirty' techniques for injecting, but also can be down to just bad luck.
Try not to worry and get on with the second injection.
Thank you all for the feedback. I’m happy to say that treating baby Star with betadine twice a day helped and the abscess is completely healed now and she did get her vaccine booster and is good for the year.
Sad to say all my goats ended up with a lump from this CDT vax and my adult dwarf doe Lizzy ended up with an abscess. Even though all my vaxx needles were new and sterile, I even rubbed alcohol on the site before my friend administered. I will not be using that brand of vaxx again.