Is it normal for team leads to frequently text their associates?

So I am dating a team lead at my store but I recently found out he's been texting one of his associates, he tells me she texts him for "work related stuff" but today I seen on his phone she texted him "hi" so when I expressed my concern he blocked her saying she constantly rants to him about coworkers and such but idk it just feels suspicious... He showed me the messages and she did in fact text him first but I find it strange how a associate can just rant and talk to their team lead off the clock because if he agrees with her or just is very friendly wouldn't that be showing favorism? So between that and wondering if I'm being cheated off I'm stressing a lot lol