'She graduated from college' and 'She has graduated from college' give you exactly the same information, but they refer to different time periods. 'She graduated from college' is past simple, and it tells you something about past time. If you use this tense, you mention or imply a specific past time. For example: '2010 was an important year for Mary. She graduated from college, started her first job, and got married.' All of these events are fixed in the past. 'She has graduated from college' is present perfect, and it tells you something about the present. For example you might ask 'How's Anna?' and receive the reply, 'She's fine. She has/She's graduated from college now, but she hasn't found a job yet.' This describes the person's present situation. Note that you can never use a present perfect construction with past time reference. You can say, for example, 'She graduated five years ago' or 'She graduated last summer' or 'She graduated in 2014', but you cannot use 'She has graduated....' with any of these time references.

1. She graduated from college. The above sentence is in Simple past tense. Ideally, it would sound better if there is an element of time. When did she graduate from college? The answer could possibly be last year, in 2000, many years ago. For example, She graduated from college in 2005. Perfect example of Simple Past Tense. 2. She has graduated from college. The sentence is in Present Perfect tense. Time is immaterial, or you have know idea of time. The fact is that She has completed the course. It may be recently, just now, already etc. So, you can say "She has recently graduated from college." Which sentence you use will depend on the context. I hope it helps.