Her bits will swell a lot when she is in season - although slight swelling and darkening may well be a sign she is coming in.
Our youngest has just had her first season and DH was convinced her pieces were so swollen they were almost taking on a life of their own
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A season lasts about 28 days; the first day of bleeding is counted as day 1 of the season and it's a good idea to note the date down in a diary. Bleeding continues (usually) until ovulation where it sometimes dries up and sometimes turns a bit watery and a strawy colour. Ovulation in an individual bitch can happen anywhere between day 7 ish and day 21 ish. Ovulation is the only period of the season where a bitch can actually get pregnant, and the only part of a season where she will behave like a pole dancer to get at boys. Bitches have even been known to scale fences, so keep a very close eye.
Some bitches bleed again after ovulation, and some don't, but you can be certain that she will be 'in season' for about 28 days in total.
For that whole period she will smell amazing to dogs; but at any time other than ovulation she is likely to be very stroppy indeed with any male dog who gets too frisky.
With the possessiveness; as she is still a puppy really and it does sound as though she is building to a season so has hormone mayhem going on in her body, I would jolly her out of it. Don't confront, don't bollock, just lots of high singsong nonsense - doesn't really matter what the words are, but the aim is to reassure her that there is nothing to be worried about - don't forget she is looking to you for a hint of how to react to the complex changes in her body.
Jolly her out of sulking - long walks, training sessions, games in the garden. Distraction is the key to getting her out of her confusion.
As long as she sees that you aren't at all worried about what's going on, that life is carrying on around her she will likely snap out of it. If the toy issue continues to develop, take them all away for a wee while and carry on jollying.
If there is no sign of blood and she remains odd and off her food I would get her to the vet tomorrow or the day after and check out a UTI. Is she drinking or weeing more than normal?