Alphys is either pan or demi if what mettatons reaction when you say you don’t know who she has a crush on holds any truth. he says

CORRECT. DR. ALPHYS HAS A CRUSH ON… THE UNKNOWABLE. YOU SEE, ALPHYS BELIEVES THERE IS SOMEONE OUT THERE. SOMEONE WATCHING HER. SOMEONE SHE THINKS IS “CUTE” AND “INTERESTING.” HELLO, THEORETICAL PERSON. DR. ALPHYS LIKES YOU. TOO BAD YOU ARE NOT REAL.

Meaning she can be with either anyone, or she can be with the right person when she finds them.

But yeah, she also possibly had a crush on asgore and mettaton as well since all answers are correct.