Two ways to set alarms...."I'm gone" mode, which has a delay. Usually mild beeping for 30-45 seconds to give you time to disarm. Then there's the "I'm home" mode which immediately jumps into full blown alarm when triggered. This is likely what she was set on. My question is, where is the panel located? The one I use most frequently in my house is in my bedroom, so if they are similar...he would be headed that way. Next question, did he announce himself? Or did he hit the door handle to the bedroom and BLAM!? Last question, did the boyfriend escape unnoticed?