As we all know, Victor and Elizabeth have been pretty well betrothed since they were children. They grew up as siblings. Elizabeth owed Victor’s family quite a lot, when you consider the fact that she would have lived in poverty, had the Frankenstein’s not taken her in. As a character, Elizabeth was simple and obedient. While it is possible she was simply a good person, it’s unlikely that’s all there was to Elizabeth. My theory is Elizabeth had a secret, which is why she was so nice to the family. It was out of guilt. They wanted Elizabeth to marry Victor, but Victor left her and couldn’t even be bothered to write. No matter how she may have originally felt, feelings do fade. Especially when communication has died and there are better options around. Henry Clerval for example. This option makes the most sense to me, not only because he is a good guy and they have a lot in common, but also because he is another character that goes out of his way for Victor, even though they had long since stopped talking. I think the reason they were both so good to Victor, might have been the guilt of betraying their childhood friend and less to do with selflessness. Face it, they make a better match then Victor and Elizabeth ever could. After everything that Victor did, if Clerval and Elizabeth were never together during their lifetime, I certainly hope they try it out in the afterlife.