LDR gf hanging out with a new random guy: boundaries?

We dated for a couple of months before we realized we loved each other and then I had to move to a different country for 8 months now and I ll be back to live with her in 2 months. She s doing an internship at a company and she met this intern guy who was kind to her, but the guy finished his internship after the first week she was there, so they only saw each other at work for a week. On his last day, he asked her out for a beer as it was his last day but just the two of them. I thought OK this is a goodbye so no big deal. but the guy lives in the same city and he asked her out again on my gf's birthday and he was going to give her chocolate (!). Apparently they have been texting since then (don't tell me how do u know? you think otherwise?) I told my gf that I m not comfortable as why hang out one-on-one with a guy you just met last week at bars and he knows about your birthday, so she says I was feeling lonely so I said yea we could meet at a bar but you are right I will say I m not feeling well tonight. The question is: given that the guy knows she has a boyfriend, are her and his behavior disrespectful as I don't think they stop texting and he ll have other occasions coming up next weeks?