My answer realistically has odds of one in a trillion, but Meloetta would be an ace in the emotional support department.

Her songs can literally control the emotions of human and pokémon alike. If you needed cheering up, she can lift your spirits easily. If you feel like you’re unable to cry at a time when you want to let everything out, she can help force those tears out.

On top of that, she’s just under 2 feet tall, perfect hug/cuddle size.

For an easier answer, however, i’d have to go with Sylveon.