I think "Something Blue" is a lot like "The Wish" in that the people making the wish had no idea that what they said was going to actually happen. She would be eligible to be forgiven since she did not realize it was a spell nor did she intend her words to be carried out. The spell that she did cast had lasting results - Spuffy became the dominant romance for the rest of the series, Xander remained a demon magnet with his romance with Anya, his kidnapping by Lissa and his eventual marriage to Dawn in the comics and Giles remained behind the power curve in everything he did thereafter with the exception of opposing Willow herself with "I'd like to test that theory".
The last we see of the original computer geek Willow is in "Gone" when she uses her computer skills to save Buffy from disintegration even though a spell would have been faster and time was of the essence.