Complex sentence: Chesney begins dating Sinead Tinker (Katie McGlynn), however she ends their relationship when she realises that he still has feelings for Katy, and that he is probably using her to spite Katy.
Split into simpler sentences: Chesney begins dating Sinead Tinker (Katie McGlynn). However, she ends their relationship when she realises that he still has feelings for Katy and that he is probably using her to spite Katy.