DO NOT KEEP A BIKE THAT YOU ARE NOT COMFORTABLE ON. BEEN THERE, DONE THAT. DO NOT RIDE A STEM SHORTER THAN 7CM. Yes, shorter bars, stem, etc. can make it kinda sorta work, but they compromise the handling. If you wanna get more aero later on the trek you can always lower or lengthen the stem.

I think you have two options, try the smaller orbea (at 5 foot 2 I can't imagine you NOT on a bike with 650c wheels, I am 5 foot 4 and require either a 24" front or 650 wheels), or return it for the trek. It seems to me that you would have better luck with a return by bringing it in sooner (while is still 'new') rather than later, so if it were me I would return it today and buy the trek. Fit is more important than componentry.