My neighbor's sons (two different neighbors, two different kids) got the vaccine and they both did get a "mild" version of the chicken pox. Lasted less than a week and neither got a fever or anything. Up until then, I had never heard of such a thing. They both took their boys and and they were told it really wasn't that uncommon. However, next time she is on amoxicilling, I would definitely watch to see if she rashes again - I have had allergies "spread" so I wouldn't rule it out.
As a mom who had 2 kiddos hospitalized with chicken pox (one the vaccine wasn't really available yet and the other was scheduled to get it and got the chicken pox the week prior to the appointment), I am envious (and happy, of course), that this option is available to kids :)
Good luck!