My sister is a FO for BA and she gets 1 day off (at the location that she has flown to) on most flights over 7 hours
If you think about it ali8b.. there's almost no other way any airline can roster long haul work.
Her 7+ hour one way flight is a 8-9 hour working day, so unless you're working under some insane regulations, doing an "out and back" in one shift isn't an option, she's at least got to have the night off at destination. However the company (any company) want the aircraft turned round ASAP so they're not going to leave it on the ground until she's had her night off, another crew will take it straight back to London. As a result your sister gets a 24 hourish slip whilst she waits for the next day's aircraft ( but as Top Bunk points out it's not quite a "day off", there's a sting in the tail). There are sometimes variations, especially if company has a lot of flights to the destination (e.g. JFK in BA's case) but the answer to your question is generally, yes, that how it works for Longhaul crews at most airlines on "shorter" Longhaul trips.
That said as has been mentioned sometimes the company's schedule demands more time off ( because there isn't a flight every day) or sometimes the flight time is so long that the regulations demand a genuine clear day off/two nights off, between sectors.