I think it'd be best to separate them.
IF the female were to take (kinda doubtful I'm betting), it definitely wouldn't be all that healthy for her, nor successful.
Snakes are solitary creatures by nature, regardless. A 40 gallon doesn't seem large enough to allow them enough 'personal space'.
Another important note- are you planning on breeding these two down the line? It's my opinion (and I know it's shared amongst many) that keeping locality bloodlines pure is a pretty good idea. You might also have a rough time selling cross babies.
I didn't plan on breeding them and if by some chance she did have babies they would just be given to friends. I'm totally against hybrids myself. I keep a number of other snakes and have for years,but have never kept or been interested in boas or pythons till the last 2-3 years. Both were given to me by friends. I plan on moving them to a bigger enclosure sometime. They seem to have plenty of room now,they can stretch out and they seem to choose to lay with each other instead of apart and they have the room to be seperate,but 90% of the time they just lay on top of each other. I've always kept all my other snakes seperate to avoid stress,but have seen quite a few people keep boas together so i figured it wouldn't hurt. I'll probably go ahead and seperate them to avoid any problems though.