1.) Their house is such a mess! - such - followed by a modified noun - article + noun adjective + nounOriginally Posted by Dany
2.) There were so many people at the party! - correct
3.) I'm so hungry! I could eat a horse. This is correct, but you can connect them and make one sentence if you want to. - I'm so hungry that I could eat a horse. or - I'm so hungry I could eat a horse.
4.) Jane and Pete are such nice people! - so - followed by an adjective or an adverb - such - followed by a modified noun adjective + noun
Jane and Pete are so nice.
5.) I've spent so much money this week! - correct
6.) A present! For me? You're so kind! - correct
7.) We've had such a nice time! - correct
8.) Molly's such a clever dog! - such - followed by a modified noun - article + noun - adjective + noun
Molly's so clever. so - followed by an adjective or an adverb -
so - intensifier - can modify an adverb Molly runs so fast. Molly was barking so loudly.
(I would use "a very", but I'm not allowed to write this here)