I would not use yet and although as you have typically. "Although it is very expensive to afford, yet she can afford it" is better written, "Although it is very expensive, she can afford it." Yet is not needed, because "although" already lets the reader know that there is a caveat to her being able to afford "it". You can also say, "It is very expensive to afford; yet, she can afford it." in which case you can leave off although. "She has a lot of assignments; yet, she can do them." "Although it is nighttime, she can go outside."