Given the careful order of the children in the will, Ann fits between Margaret 1807 and Catharine 1815. Since Robert is 1810 and assuming no twins here, then Ann should be about 1813.

There's a baptism 11 Apr 1813 at Marown for Anne KELLY but the parents are "RT KELLY & JANE QUIRK" according to IGI. The IGI shows no marriage and no other children.