Bahar

On your cat being loud specifically: volume varies enormously between individuals and it does not mean anything in particular.

It is largely anatomy and individual variation, in the same way some people have carrying voices. A very loud purr from a relaxed cat is not a signal of anything beyond a relaxed cat.

The more interesting observation in your question is that she is not generally affectionate but purrs hard when she does seek attention. That pattern is common and it is worth taking at face value — cats that solicit contact on their own terms often engage very intensely when they do. Letting her set the timing is usually what maintains it.

There is no good reason to think it is tiring, and the mechanism is the reason why.

The exact process is still not fully settled, but the leading account is that purring involves rapid oscillation of the muscles controlling the larynx, which modulates airflow during both inhalation and exhalation. Critically, it appears to be an almost passive addition to breathing that is happening anyway, rather than a separate effortful act.

That matches the observed behaviour. Cats purr while falling asleep, while asleep, while eating, while being handled — none of which are compatible with an activity that demands real exertion. An animal does not do something tiring continuously while dozing.

So the honest answer is: as far as anyone can tell, it costs very little, and the fact that cats can sustain it for long periods is itself decent evidence.

On the ethics, since that is the part making you uneasy: it is a genuine trade rather than one obviously right answer, and the balance differs by place.

For outdoor access: more stimulation, more exercise, more natural behaviour, and generally fewer problems with boredom-related behaviour and weight.

Against: roads are the dominant cause of death in young outdoor cats. There is also fighting, disease transmission, poisoning, getting shut in a shed, theft, and predation of local wildlife, which in some places is a serious conservation issue.

Attitudes vary hugely by country — in some places indoor-only is the norm and outdoor access is seen as irresponsible, in others the reverse.

What is not in dispute is that an indoor cat needs the stimulation designed in deliberately: vertical space, window views, play sessions daily, puzzle feeders, and things to climb and scratch. An indoor cat in a bare flat has a genuinely worse life. An indoor cat in a well-arranged one does not.

The middle options, which is where most people in flats end up:

Harness and lead. Genuinely works with many cats, especially if started young — and at six months you are well placed. It takes patience: harness indoors first, over days, then short trips. Never attach a lead to a collar.

A secured balcony. Netting or mesh enclosing your own balcony gives outdoor air, sun and smells with no escape route. This is common in cities and it transforms an indoor cat's day.

Supervised time outside in an enclosed yard if you have access to one.

A catio, if the building allows any structure at all.

The shared balcony is a real hazard regardless of what you choose — a door propped open by a neighbour is a route to a stairwell and a street. Worth a conversation with the neighbours whichever way you go.