Once you escape the Houndoom's maw, you pant out in exhaustion as you turn towards him. You could tell that if you ran away now, you'd get away, but the Lopunny would be digested by the Houndoom, but if you tried saving her, there was a slim chance that you'd be successful, but you'd have a much greater chance just getting swallowed back down by the Houndoom. So you decide to...

• get away. It's too late to save the Lopunny.
• save the Lopunny. You can't just leave her to be digested.