lol I like option D ;)
Even kritter keepers from Petco, a 3 gallon is roughly $10, get two of those, they are heater safe, and plenty of space to decorate them.. can use a lamp to light them :) It's what I use for mine- simple, cheap, easy to clean.
There are some large bowls and other containers out there.. you don't have to use specific tanks- This is a neat idea that I saw when going through Walmart one day and saw a large glass cookie jar.. the problem is the heating of it, she will have to get used to a cord in there, but at least you can hide it with plants.
A 1 gallon is enough space for them, I would go a little larger if you could for the fact you can do more with it.. but with weekly water changes, they are just fine.
Bettas don't need filters, but you would have to do a weekly water change of a 100% if you forgo the filter.
But definitely separate them, they haven't fully adjusted yet, one is most likely thinking they are in the territory of the other- so they haven't gotten to the part where they will stop chasing and start biting each other yet. A small bowl with both of those in there will cause them to feel "trapped", as males will stay in a spot and mark it as their territory, whereas females move all over the miles and miles of expanse waters, only going near a male when they are ready to breed, then immediately leaving.
So once the male tries to set up territory in the bowl, you're looking at a female who will get hurt, and who will turn to the male to protect herself and hurt him.
Unfortunately, people don't understand that these guys don't live in puddles, they have miles and miles of water, and they come from areas such as Thailand, where it's hot. Silly store clerk just wanted a sale. I suggest not going back to that particular store when you go to get the other tank, don't give them any more money- most likely the store clerk new exactly what they were saying and knew that within a week or so, you would come back to either get a replacement fish, or another tank once you learn the truth and would get even more money off of you from their misinformation.
Good luck with everything.