When they close the distance and go melee (which is most likely since Barda usually enjoys close quarters combat) the team should be able to take a majority.
but that was not your average heimdall, he had some of the odin firce backing him, they had one fight were they were on average showings an it was either a stalemate or heimdall won, in hand 2 hand tho
No they wouldn't take a slight majority, they would maul her. Betty is a high class 100 even without the Wishing Well. Heimdall could give Big Barda a good scrap, while Betty would defeat her straight out. Betty was able to punch through a dimensional barrier, which is an absolute ridiculous feat if you were to think about it for a second. She's also quite skilled with that sword of hers that was made in Asgard, and enchanted with a portion of the Odin Force. It's the same sword that was able to pierce the Hulk's hide in the Dark Dimension.