Your cycle can take a while to adjust when the hormones wear off, I use a different type of contraception that involves a hormone impregnated plastic rod that is inserted into my arm and my period always goes a bit strange when I get a new one inserted. I will go 6 months without a period, or go 3 months worth of unusual cycles, like short gaps in between, breakthrough bleeding and continual light period for more than 2-3 weeks - (Sorry if this grosses anyone out, i thought it was best to be honest for the sake of the OP)
All i mean, i guess, is that what happens to the person who gets the procedure done or any type of contraception, the symptoms and effects aren't always going to be text book and that sometimes the results can really vary person to person. I don't think you have any cause to worry at this stage, but if she isn't getting her cycle within the next few months, get her to book in with her gyno or GP.
When I got my first one installed, I had no period for almost 12 months and I thought it was awesome. I made sure that my partner and I followed safe sex practices just in case for the first couple of months and always have the new one installed and old one out a few months before they are due to be removed and re-inserted.
