What is a good pet for an apartment?  

I mean if she is lonely, then something that is more cuddly and not a cage animal would be ideal. So maybe a cat, a small dog, or a rabbit. Thought rabbits are required to be in a cage when not being supervised. 

Cats tend to be the number one pet for apartments as they don't need as much space, are quiet, and can be very affectionate. I would tell her to get a cat or kitten. 

I think money, time, and space all need to factor in. A lot of people get cats because they are easier than dogs but if your friend doesn't spend a lot of time at home, the cat will get lonely. Maybe getting two would be better? 

A small dog or cat would be best I think. Though it really depends on the lifestyle of your friend, as mentioned. As well as the income level and location. Some places just aren't spacious enough for pets. Birds make great choices as well but you'd want to stick with a smaller one because of the noise.