Hi & Welcome,

Bitches can concieve usually between day 11 onwards is the general rule,although I have known bitches that will stand earlier than that,around 7 days and later, day 23,so you really need to keep her away from males for around 5 weeks.
If your Nan is not planning on breeding from her it may be a good idea to have her spayed,you then have no worries with seasons and it cuts out the risk of pyometra which can be fatal in bitches.

As for the behaviour,it may well be because she's in a new home with strange people and surroundings,different smells sounds etc.....

A good idea to get her checked by the vet,let us know how you get on....