Judging from what was shown in the episode, it seems that Penny must have lost the fight. Aside from the damage shown (black eye, busted lip, otherwise sore and hurting), the dialog implies this as well. Throughout the episode Howard has been making his usual smarmy comments toward Penny, and every time she gave him a sharp rebuff. After we're shown Penny's battered condition, Howard again makes such a comment, but this time Penny just meekly replies "Thank you, Howard." He turns around and says "Oh yeah, that filly is BROKEN." Penny doesn't really react, which seems to me to be indicative of a girl who's used to dishing out the punishment finding herself on the losing end instead.
In the meantime, we hear Alicia upstairs having sex with the CSI producer who's her new boyfriend. This at least implies that she came out of the fight in better shape than Penny, and might also indicate that she's celebrating her victory. Now, if memory serves, in the episode we never got any info about Alicia's background, so it's possible she also had some previous fight experience. That certainly seems to me to be the most plausible explanation for the outcome we're shown.
If I was writing this as a fight story, that would be the approach I'd take... Penny knows she's a tough girl and also knows from her many failed auditions that most actresses are creampuffs. What she doesn't know is that Alicia has some significant catfight history, and underestimating her leads to a disastrous and unexpected defeat. Judging from Penny's stunned, shellshocked reaction at the end of the episode, this is pretty rare, maybe even her first real loss, which again could make for an interesting story hook. On the other hand, seeing her defeated that way would probably remind Leonard how much he cares for Penny, so the outcome does serve in that way to restore the status quo. I'd end with a postscript explaining that Alicia soon moved in with the CSI guy, which is why we don't see her again.
I could see at least a couple of good possibilities for a follow-up story. The obvious one is that Penny again encounters Alicia (probably at an audition somewhere), and the two wind up fighting over a part. We have seen that despite her confident exterior, Penny clearly has secret insecurities, and I've got to think that having to face the one woman who humbled her before would be doubly challenging for her.
Another less obvious but rather interesting option could be that Sheldon's sister Missy crosses paths with Alicia, leading to a fight between the two. They're about the same size, and one gets the impression that she was rather a tomboy when they were growing up, so she could probably scrap as well.
Actually, thinking about it, the whole thing could be done as a full story arc... Penny loses the rematch described above as well, perhaps in a more humiliating fashion, which really shakes her confidence and leaves her completely intimidated by Alicia. This is illustrated when Penny goes to an audition full of optimism, sure that she's got a great chance of scoring her important break, only to be confronted by a smug Alicia. Penny's poise collapses and she backs down, completely unnerved, finally leaving without even auditioning and instead just sits crying in the car before heading home.
Missy and Alicia then encounter each other as in the second scenario, and though she acquits herself fairly well Missy also eventually fails and is humiliated as well. (I'm thinking that in each fight we'd see Alicia going even farther to score a win, revealing initially unsuspected reserves of cruelty and sadism.) Sheldon somehow learns about the fight, though he doesn't realize it was with Alicia, and he approaches Penny privately to ask for help. Penny is so touched that Sheldon has come to her out of concern for his sister that she agrees, only to find to her chagrin that she has agreed to fight Alicia. She then has to try to find the courage to once again go and confront her nemesis.
OK, maybe I've gotten a little carried away there...
-JM
