How do I handle this better? I think my fiancee plays games too often.?

I want to get some honest, polite, constructive opinions on how to better handle something. I love my fiancée so very much. She is the most important thing in my simple life. She owns my heart completely and I just want her to be happy and successful, especially if something were to happen to me. (She is young 25 and I am much older) and she is admittedly addicted to online horse related SIM games. I honestly believe it’s part of why she is struggling in college, but she thinks it’s mainly her depression that is affecting her grades. But this woman is brilliant. I have always told her she is the smartest person I know. She reply’s I must not know very many smart people, but I do have some very intelligent friends. One speaks five languages four of which he taught himself and she is smarter than he is. The problem is I think she plays too many games too often, partly because of her depression but I think the games lead to less study, lower grades and consequently more depression. So I have been trying to get her to reduce the time she plays her games. Now I’m afraid I am getting obsessive about it. I’ve been keeping track of the games she plays and how often she’s on in an effort to hold her accountable I guess and try to make her realize she should play less. I have told her that she should only be playing when she has her class work done but I think she uses it to cope depression anxiety and stress too often. I do think she plays too many games too often. But then, I do not play games, so I guess it’s hard for me to understand the allure. Maybe I am being too sensitive and too critical or her. I’ve seen her online playing several games at once (I have a list of 12 that she has played this year although I think she only plays 3-4 consistently) and she sometimes plays for several hours. I feel bad though because it seems like I'm always getting on her for playing them. I realize I'm her fiancé not her father, but I am afraid she will not get into vet school unless she really reduces the amount of time she plays. I also realize she could be addicted to drugs or alcohol or many more destructive things. One of the reasons I’m so worried is because I have a very addicted personality and I have been addicted to alcohol and other destructive behaviors in the past and I’m worried she will ruin her college career. I know how my past addictive behaviors and coping mechanisms destroyed my first marriage and literally almost destroyed my life .Is there anyone out there who realizes they are addicted to games? Are there any other significant others whose significant other/loved ones are addicted to games? How are you handling it? Please help me to do a better job of supporting my fiancee. I want to do the right thing. Please don’t be mean because I’m not trying to be a controlling fiancé or keep her subordinate or anything like that. I am only trying to be a good fiancé and friend.