You're not being paranoid at all. After all, it does seem odd that should would get a completely new number to contact someone from "work", let alone become defensive about it. Since you've been together for so long, you've obviously come across up and downs, but you do seem responsible when you approach important decisions and you want the best to come out of your relationship with her. You should never deal with anyone putting you down, and it may seem like she might be asking for some space, not necessarily for the best reasons. Try to talk to her and put things out in the open, once she realises your concerned about what's going on she might think twice about what she's doing. If not, this might be the moment to think about your relationship, and if you'd like to pursue it further or not...