Your female is one macho lady. xD;
I have tried spawning bettas in small basins before (one food tray converted to a betta pan, and the other in a 1.5g mini glass tank). Out of approx 4 times, I have had 2 successes. I figured that regardless the size of the breeding tank, the chance of success still depends on the readiness of the pair..how much they wriggle-dance at each other, vertical stripes, eggy-ness and the male's enthusiasm at bubblenesting. I think it is just that in a small environment, it happens faster if the conditions are right, but you also need to monitor them more closely and quickly pull out the female at the earliest sign of trouble. Both times I had IAL and plants for shelter. I almost lost my red dragon HM girl once because she tried to commit suicide by jumping off the basin onto the floor. I didn't know she was so desperate to get out of there, haha. Thank god my mum found her alive in the morning. x_X
Plus, even if the spawn is successful, you'd still worry about having to transfer the fragile babies into a larger tank when they become free swimming, risking temperature/chemical shock and all. But you would have to do it soon anyway, otherwise you risk an ammonia spike in such small volume of water..that was the dilemma I faced when I first encountered it.
TBH, I find this method a hassle, and I won't do it if my 10g wasn't occupied already..
All the best in your next attempt~