Yes, S1 Kelly was proud of her sexual experience. I miss that. It changed later. I think that in S2 she was already sort of ashamed for that. It possibly started with Kyle and his refusal of "light fun" she offered.
I do not remember Andrea giving Kelly guilt trip about her sexual experience. What did she say?
And Kelly did offer information about being rejected by Brandon to cheer her up, so I don't see why it would be a big deal if it did cheer her up
I don't think she was necessarily happy about Kelly being rejected by Brandon, more feeling like... she was not alone in an unrealized crush. And she got bigger comfort in Kelly's point that she did not have to necessarily lose her virginity at any cost.
Brandon was an ass to Andrea in that episode. Kelly was cool.