Ok, a number of differing thoughts on this case...
Re the above. Excess steam tripped the alarm? Hmm, same thing happened at a hotel where I was staying last year - the football team also staying there apparently thought they could use the shower as a sauna, and when they opened the room door, it tripped the alarm.
My question would be - has this ever happened before at the lab? If so, especially if it had happened repeatedly in the past, the steam could have been generated intentionally knowing it would trip the alarm. That would indicate the individual who tripped it was very familiar with the building.
Some other things that have crossed my mind. The cell phone. It seems unlikely that a girl who was presumably doing all those last minute things with her wedding would leave her phone behind. However - is it possible that cell phones might not have been allowed in the lab? If so, that would explain it.
The animal testing and stem cell angles are definitely worth checking into. Also - could she have had access to any controlled drugs that someone might have attacked her to get?
I am not entirely convinced that there is no chance that she wanted to disappear. Could her parents have been pressuring her into marriage? I know there are some cultures where women are expected to marry - I'm uncertain what her precise heritage is, but could this be a factor?
Another possibility - I saw mentioned earlier that she was apparently the driving force behind the wedding? How might she have reacted if she found out the boyfriend had been unfaithful? Could she have felt embarrassed enough to take off?