the decision to pay for a friend's meal when dining out on their birthday is entirely up to you and your personal relationship with that friend.
In many cultures, it is considered a thoughtful and generous gesture to treat a friend to a meal on their birthday. It can be a way to show appreciation for their friendship and make their special day even more memorable. However, not everyone might be comfortable with this, and financial considerations could also play a role.
Before offering to pay for your friend's meal, consider their preferences and the nature of your relationship. Some people might feel uncomfortable accepting such an offer or might prefer to split the bill. The best approach is to communicate openly with your friend and understand what they would appreciate the most. Regardless of whether you pay for the meal or not, the thought and effort behind celebrating their birthday together will likely be appreciated.