If you like a guy and he likes you and his grandmother passed away a few days ago should you be upset if you found out he has been texting another girl about it?

It doesn't sound like you are steady dating with this guy, so he can talk to whom he wishes. I have no doubt he is very upset over the passing of his grandmother and has to talk to someone. Ask yourself if you made the effort to text him or even phone him and let him discuss his feelings with you. You can still do that. People have a tendency to go to other people who reach out and are there. Make yourself more available and mean it! Sometimes just listening or putting an arm around someone when they are grieving is a big help.