Am I being reasonable or am I way off base?

My girlfriend and I have been together for 9 months now and we are exculsive and love each other. My issue is this: She has a guy friend who she used to have very strong feelings for that she still has contact with on a regular basis. He lives 1,500 miles away in another state so their contact has only been phone/text/email. This guy has also said negative things about me in the past. Back in May my girlfriend and I broke up for about a week. Since we have been back together she has not told her guy friend that we are back together. She says she does not want him to know because she thinks she might have a financial opportunity with him and that if he knows he might somehow retaliate against her and deny her this opportunity. She also has told me that she sort values his "approval" and doesn't want to hear him say negative things about us being together. During our relationship I have always tried to be there for my girlfriend and make her my priority. I am basically there for her whenever she needs me. My question is this: Am I being unreasonable in my thinking that her having a friendship with this guy is not cool? They have known each other for years, and we've only been together for 9 months . Or am I being overly sensitive in thinking that this is not cool. I just think that when you are in a relationship that it's almost impossible to have a really good friend of the opposite sex who you talk to frequently and especially when that person has said negative things about you. I would love any input or feedback. Thaks!