Hi again everyone, and thanks again for all the extra advice. I’ll try to answer everyone's questions

Breeding - her damn is Dutch Warmblood KWPN registered (keur or ster grading?) - Cali has TB, Gelderlander, Holsteiner, Selle Francais in her lines, and her sire - Talents Asa - was 'British Warmblood' (although his parents were both Danish Warmblood) and has Trakehner, Hanoverian, Swedish Warmblood in his blood lines.
I worked out, theoretically, that Tutti is made up of the following:
TB 22%
Gelderlander 19%
Trakehner 19%
Hanoverian 19%
Swedish warmblood 12%
Holsteiner 6%
Selle Francais 3%
Not sure if any of these breeds stand out as 'problem' horses?
I will keep a diary, as it’s hard to remember the good things – like I just remembered the other week she walked through a stream (after much persuasion and making the dog walk through several times!) before Cali would even go near it! I also think she, or Cali, is in season at the moment as well, so that could be contributing to it.
Paddock – she is on a small paddock by herself during the day to keep her weight down, but out with the other two at night. I do think it has helped with the ‘separation’ problems as she doesn’t seem bothered now if Cali isn’t in sight.
Shoes – I think I will get them put back on when the farrier is due shortly – at least it will rule out the feet if she does continue to behave the way she does.
I will up her work – I can lunge before riding but at the moment I wouldn’t be able to exercise twice a day separately. I did actually get back on and ride today – just in the school for a bit – she was fine – trotting around calmly but then after about ten mins she decided to start stopping

having said that, she seemed to be quite affectionate towards me today – like what happened on Tuesday had never happened – that’s what is good about Tutti – when something bad happens or she heats up the next day she’s back to her loving, characteristic self.
If the behaviour carries on after trying lunging, more work etc, after a couple of weeks I think I will investigate the ulcers again – it’s just the vet was so adamant because they healed so quickly with the antibiotics that they wouldn’t come back again because the bacteria had been treated. Only prob is ulcers are excluded from her insurance now

Thanks again for all your great and understanding advice

it’s really helped and I don’t feel like a ‘bad’ owner thinking the things I have done about her lately.
Will keep you all updated,
Gemma