What sundew is it? Do you have a picture. Many CP's will grow together just fine for several months but if they gave different requirements, then they need to be accommodated. VFT's are temperate plants and need a dormancy. Some sundews are as well. But there are also sub-tropical and tropical sundews that need to be kept warmer.

Hmm, I didn't think about the dormancy period. The sundew's too small for me to easily take a picture of, but I'll see what I can do.

If I decide to separate the plants, are there any special tricks for transplanting them? This is my first experience with carnivorous plants, so I don't really know how delicate they are.

As a general rule, prepare a pot first and create a small depression in the media. Use a spoon and remove the plant with as much of the soil surrounding it as possible, so as to avoid disturbing the roots. Place the "plug" in the depression of the new pot and gently water to help mesh the media. That's it!