Does it seem odd to you when a girl ends up dating the old best friend of the guy she was dating?

yeah that is the way it seems to me too.

I have a good friend named Sonnier. Sonnier dated Eric for 4 months. In those last few weeks there was a lot of arguing because sonnier figured out that Eric had lied to her about being a virgin. Now, she wasn't mad that Eric wasn't a virgin. She was just upset that he lied to her about it. She'd have preferred if he had said, "I don't want to talk about it."

What made it worse is that apparently he talked about how hard it was to maintain being a virgin. How there was a lot of pressure to give it up. Basically, several conversations ended up being complete lies.

Then it got worse, we found out he lied about much more than being a virgin. He lied about how long it had been since he was last with his girlfriend. He also, pressured her a lot to be more sexual. Which was weird for Sonnier because she is a virgin.

Anyways, they broke up about 3 weeks ago and now she is dating Calvin who was Eric's best friend. Calvin was also interseted in Maria for a while. Maria was Sonnier's best friend. I say was because she is convinced that Sonnier is dating Calvin in order to be mean to her. Her sister, who came along to visit, thinks that Sonnier is doing it to get back at Maria for how she acted.

While, Maria and her sister, Bina, visited Maria seemed to largely ignore Sonnier. She was sick but, as Sonnier told me and I later saw at the salsa place we went to, she seemed to have no interest in doing anything with Sonnier.

As far as I'm concerned...sonnier was wrong to respond to Calvin's affections.
Calvin was wrong for ever kissing her or for showing interest in Maria when apparently he really wanted to be with Sonnier. I started talking to Eric again and he admitted that Calvin already told him in March that if Eric screwed it up with Sonnier he would go after her.

So...I think Calvin is largely out of line here. Like he was when Eric and Sonnier were fighting earlier.