Is it okay not to tell someone something because you think they’ll disapprove? Assume it’s something that doesn’t affect their life, only yours, but you know they like hearing about your life and you know their feelings will be hurt if you don’t tell them. Do you have an obligation to tell them?
realsocialskills said:
There are very few things you have an obligation to tell other people about when they’re not personally affected. In fact, off hand, I can’t think of any. (Although, it’s not always 100% straightforward what does and doesn’t directly affect someone. Some things that seem like they don’t actually do.)
That said, outright lying about something the other person is likely to find out about tends to backfire, because it can have a corrosive effect on you. It can make you feel like you must be doing something wrong if you have to lie about it, and it can make you anxious about what will happen when they inevitably find out about it. Sometimes it’s a good idea anyway, but often it is not.
If someone is personally offended that you keep some parts of your life private, that’s a major red flag. It’s a sign that this relationship has bad boundaries.
No friends tell each other everything; no one approves of everything their friend does. There are always at least a few things that it’s better not to discuss. 
In mutually respectful friendships, both people understand this and respect one another’s privacy. If someone expect you to tell them everything and gets upset when you don’t, they’re being controlling. They’re not treating you as an equal.
And it usually gets worse over time. If someone can convince you that you’re not allowed to have any boundaries or privacy, they usually keep pushing.
Some people who do this start acting right if you assert boundaries and refuse to tolerate it when they’re breached. That doesn’t always work, though. Sometimes you can assert boundaries enough to make the relationship work even if they never really respect them willingly. Sometimes that doesn’t work and the friendship can’t be safe even if you really, really like them in other ways.