URGENT!! Trying to figure out if my girlfriend is being honest with me over the text she just sent me?

no. she will think you are spying on her or something. try and be more subtle. maybe mention the other guy and say something like "that guy who was at your place yesterday seemed nice" or ask something about him and maybe she will tell you whether he is still there or not. if you're still worried, then you obviously don't trust this girl and maybe it's time to just ask her outright.