We tend to dream about things we've already experienced or things that have been active on our mind. If you talk to someone on a regular basis its quite possible they'll appear in dreams. Dreams are a way for our minds to 'clean up' and put things in perspective, which is often why we wake up feeling better after a stressful day. You're not going 'mental' at all, everyone finds it difficult, sometimes, to differentiate between dreams and reality, especially if the dreams concern people or activities we encounter everyday.