Should I marry my girlfriend? or leave her?

We’ve been 2 years together now and its been mostly amazing. We have so much fun together and we are incredibly attracted to each other. However the time has come to decide on whether I want to marry her or not. We live in a semi-conservative country and girls gets marriage proposals from acquaintances and family friends – thats the traditional way of getting married.
My girlfriend is gorgeous and she gets lots of those but she keeps saying no. But now she has a lot of pressure from her parents because she’s 27 (I’m 25). So now the pressure is on me to propose.
She had done her best to keep those pressures away from me for a while now, but its hard now. I have my full intentions on marrying this girl and I love her so much.
However I have my doubts concerning her emotional maturity which lead me to jealousy and distrust. Having all this pressure on proposing drove me to dig deeper into her personality and secrets. I’m not proud at all of what I’ve done but I thought this the only fast way to know if I’m willing to propose to this girl. What I did is take a look at her online activity. I have found out that 10 months ago and spanning up until 5 months ago (5 months period) she had been considering other men (that proposed) in her life. And whats worst is that she had been fantasizing (and dreaming) about a married guy at her job (googling his name and sign nearly every week, and looking for stuff on seducing a married man). However I know for a fact that she didn’t cheat on me.
I also think that what I’ve saw could be just a phase she was going through. And for the past 5 months every thing have been great between us and she listens to my advice regarding her emotional immaturity. I didn’t mention any of my findings to her yet, and I don’t think she’ll take it nicely.
Any advice is greatly appreciated.