I haven't personally noticed any hints of Sinead having a thing for Tyrone, but her disinterest in marriage might be the beginning of the end of her and Chesney (so clearing the way for him and Gemma).
The writers must have short term memory loss as last Christmas sinead thought the ring tyrone got fiz was for her from ches and got all excited thinking it was a proposal for her. She was disappointed when tyrone corrected her and got drunk because of it