Sorry to disagree but the only tetras that can be safely kept with bettas are the Cardinal Tetra. All the others are known to be fin nippers and the bettas do not see them as threats so will simply allow them to do it and end up with infected fins.
Mollies have long flowing fins and can be mistaken by Mr. Betta as another of his species and attacked as such. So it would not be advisable to put them in with a betta or for that matter any other fish with long fins either.
Bettas are not raised in tanks with other fish and do not recognize the rights of the other fish to be in the same water with them. This is one reason why they do not do well in some community settings. The ones who do are usually the last fish introduced into the tank and have small nocturnal fish that do not get into their way. Fish with long fins, territorial fish and semi-aggressive fish, and fish that are related in any way to bettas should be definitely avoided. A partial listing is:
THESE FISH ARE NOT GOOD TANK MATES FOR BETTAS
Platies .... resemble female bettas
Guppies
Mollies
Swords
Rams
Gourami
Sharks
Barbs
Cichlids
Angels
THESE FISH ARE BETTER TANK MATES FOR BETTAS OR AT LEAST HAVE PASSED IN MY TANKS
loaches -smaller ones particularly (chain or dwarf loach, kuhlis, angelicus, yo-yo) tank size depending
plecos - (clown, queen arabesque, common) tank size depending
otos - no more than 2 per 5 gallon of tank size
cories - tank size depending
Hope this helps