Mitton seems to be a fairly common name in the area, judging by the records I've seen. I can find no parish burial records in Yorkshire on FindMyPast for a Sarah Mitton in between 1717 and 1720 so while I can't be certain it looks likely they are separate children.
I've found what I think is an image of the actual 1717 baptism:
'November 24 Susan daughter to Daniel Mitton of Walsden, Weaver.'
There's a series of other children born to a Daniel Mitton in Todmorden on FindMyPast, sadly most are just transcriptions, rather than images. There is an image for a Betty Mitton born to Daniel of Walsden. in 1719. Interestingly this page also holds the baptismal record for a John born to 'Daniel Mitton of Todmorden'. suggesting that there are at least two Daniel Mittons having children in Todsmorden at around the same time.
Edit: Do you have a full list of Sarah and John Wadsworth's children? It might be worth looking for potential repeated names in these earlier sequences of births.