Is it ever right to say something when you're worried about a friend?
Yes — but speak about what you have seen rather than what you have concluded. "You seem to check your phone a lot when we're out, and you look worried afterwards" lands very differently from "I think he's controlling you," which usually makes someone defend the relationship and distance themselves from you. Name the behaviour, say it concerned you, make it clear you are not going anywhere, and then let it sit. If what you are seeing frightens you, encourage her to speak to a counsellor or a specialist support service; staying reachable matters more than being proved right.
How do I stop comparing my relationship to couples I see online?
Start by noticing what the comparison is actually telling you. Envy of a couple who laugh constantly often means you want more lightness; discomfort at a couple who seem enmeshed often means you want more room. Treat the reaction as data about your own needs and then take it to your partner as a request rather than an accusation — "I miss laughing with you, can we do something silly on Saturday" is a conversation, while "why aren't we like them" is a verdict. It also helps to mute the accounts that leave you auditing your life instead of living it.
The most honest thing most of us can say about someone else's marriage is that we weren't there. Spend the attention you were about to lend a stranger on the person sitting next to you instead. That one you can actually ask.
