Is the ***** about to come into season?

Yes, and yes. If you can contact your sister, ask her when she was last in and what her normal cycle is, although something like a change in her normal routine, can bring a b itch in earlier than perhaps usual.

For sure separate her, now, from all other dogs, even her companion because things can get a tad tense when one comes into season!! Fighting isn't beyond a possibility. If she's squatting more than usual, then it's quite possible she is already in season(or has a UTI!!). Have you done the tissue test - holding a white tissue to her vulva to see if there is a coloured discharge at all? If her vulva enlarged - that's another sign of impending season.

For now, at least until you know what's going on, I'd stop taking her out off your property just in case. Or take her off in your car to somewhere quiet, keeping her on a lead! And when you take her outside in the garden/yard to empty, at least have a lead ready to snap her on, should a strange dog show up.

In case you don't know, her season will last 21+ days, with the most important phase to keep her safe - days 10 - 14. But some bitches will be ready to mate sooner than then, and some later.

ps You should call your sister - she may want to get home to deal with all this herself!!

Add - There is no supposed to mate in any of this - and certainly not at 8 months!!!