As voted by comments, and a PM from someone who wanted to keep their vote anonymous, the choice to get her attention has been made

You needed help, and all signs told that this mare would be willing to help a small creature such as yourself. So, you took in a deep breath, and shouted out.

“HEY!” you cried at the top of your lungs. The giantess’s ears twitched in your direction, and the mare looked about.

“H-Hello?” she asked shyly, her gaze flying about, scanning the room.

“Down here!” you shout again, and the her eyes fall on you.

“Hmm? And who is this?” she calmly approached you, that brief shyness now gone from her expression. “Poor thing, are you lost?”

“Y-Yeah,” you reply. She was a lot bigger up close. You barely managed to keep yourself from fleeing as she reached down to grab you.

“Oh my!” she says picking you up. “You feel so cold!”

It was true. Though you couldn't tell why, you were steadily getting colder. Perhaps is was winter or fall in this world? Maybe early spring?

The giant mare held you against her breast, and you cooed at the softness and warmth.

“Poor thing, you must be so scared. Well don't worry, I'll put you somewhere nice, safe, and warm.” she grabbed you by the scruff of your shirt and lifted you up. At first you thought she was going to drop you into her cleavage or something like that, but soon you found yourself suspended a bit above her head. Her eyes were closed, her mouth was open, and a sense of fear gripped you as she began to bring you to her gaping maw.

Author's Note

Well, you're all in quite the pickle now. Here are your choices:

Fight back

Accept your fate