I'll try to keep it short!
FIL met his girlfriend two years ago. She's very nice in general, and the children really like her. She's young, the same age as DH actually (late twenties), and FIL doesn't want any more children - which she has accepted and is now very sure that she will never have children. I'm not sure, but I think this may be relevant.
Pretty early on though I started to feel a bit uncomfortable with certain things she'd do/say. Overstepping boundaries. Not long after meeting DS she designated a special nickname for herself that he could call her. There have been lots of little overfamiliar things which have made me cringe a bit, though nothing as weird as recently.
She and FIL asked if they could take DS to Legoland for a birthday treat. It was really lovely of them, DS was really excited as he'd been dying to go. The day came and they arrived to pick him up.
FIL was busy in the kitchen with DH so I went through a list of stuff I needed to pack DS for the day and realised I'd run out of plasters (DS trips over a lot), so I asked her if she had a first aid kit in the car just in case the inevitable happened and he skinned his knee. The look she gave me was scathing. She then said, "do you think I don't know how to look after four year olds?" She is a primary school teacher, so I don't know, maybe me asking whether she carried plasters with her was a slight on her professional ability somehow. I felt she was defensive
I just said, "Oh good then" and she changed the subject.
So as they're about to leave I ask FIL to make sure DS gets one of those wristbands put on in case he wanders off somewhere. FIL just nodded, but she did a massive eyeroll at me and said "yes yes we know" - again I got the feeling she was being defensive. Then they left.
They all came back and had had a lovely time, and had taken lots of photos. She was flicking through them on the phone, showing them to me when she stopped on of them all with FIL's arms round them both and said "he really could be ours by looking at him couldn't he?" - Apparently lots of people in queues were mentioning how handsome their son was, and she laughed as she told me she didn't bother correcting them, and just said thank you very much. DS is mixed race, FIL is black and she is white - so an easy assumption to make.
The most recent incident was at DS' birthday party. She started to cry, but shrugged it off quickly saying they were happy tears and told people not to make a fuss. She drove me and the children home and I asked what it was all about and she said "oh, it's just DS looked at me and I just thought 'god I love him so much' and it just set me off, that's all"
Please tell me that this notion I have of her using my children to replace the children she has decided she won't have is nonsense, or, if not nonsense then completely harmless?