You have missed some fasts of Ramadaan. You have to make them up after Ramadaan. There is no disagreement here. Do you have to make them up right away as soon as possible or can you delay them?
Some scholars said you can delay them. Others said you cannot. You have to make them up as soon as possible.
Both draw evidence from the same narration of 'Aishah which reads:
If one amongst us had to break fasts (of Ramadan due to natural reasons, i. e. menses) during the life of the Messenger of Allah (sallallaahu alayhi wa sallam) she could not find it possible to complete them so long she had been in the presence of Allah's Messenger (sallallaahu alayhi wa sallam) untill Sha'ban commenced.
Sahiih Muslim Hadiith No. 1146
She made up her missed fasts in Sha'baan. This means you can delay your fasts.
The opposition says no you cannot. The narration is evidence against you and not in your favor. She said: "she could not find it possible to complete them so long as she had been in the presence of the Messenger of Allaah." This means she had wanted to make them up as soon as possible but was not able to. Had she been able to she would have done so. Hence, one is to make them up as soon as possible and not delay them.
Two opposing opinions based on different understandings of the same narration.