Hi @Littletink_
First of all can I recomment that you join in the discussion on Topic Tuesday tomorrow night that might be helpful to you - "Caring for the woman in your life"
"Expressed emotion" is the technical name for unhealthy responses to mental illness and can take a number of forms. Some of it happens out of misunderstanding, other times it is out of fear. Sometimes these responses are valid, sometimes not but finding healthy ways to express them is vital. It is important to realise that expressed emotion from a parent or a partner does not mean that the patient is not loved.
From what you have written it seems that father-in-law (FIL) might be a bit conflicted if he is asking Ms L-T what she is doing about her mental health and then asking her about work or critising the need for meds; lack or information and/or misinformation can be the root cause.
How is your relationship with the in-laws (or as I like to call them the out-laws)? My first instinct is to see if there is some psycheducation available - if your partner is amenable - this might be a session with her case worker or psychologist/ It is important to note and reassure your partner that this can be a general session and specifics of your partners case do not need to be discussed, this of course should be made clear to the person convening the session. Wellways or other MI support services might also be able to provide this - family education has been well documented to decrease expressed emotiion, to improve outcomes for a patient and to reduce rates of relapse.
A parent is always a parent and the fact that dad still is in touch means that he probably does care. Finding a happy medium as to giving the outlaws just a little information so that they do not feel excluded can be a hard one, but I have found that giving Mr Darcys family just a little bit of info was helpful, I have not yet given them his diagnosis as it has not long been confirmed but will probably let them know that he has a diagnosis which is now stable but requires life long medication and that there is a chance he could relapse but less likely with appropriate meds.
It can be difficult to warm to outlaws in any event, but even harder when the things they say are unhelpful - one of my brother in laws was like this, but I had to realise it was his way of dealing with it and I too have had unhealthy responses at times and learning healthy coping mechanisms really helped me. I ended up sending the whole family some information about what not to say after an attempt. Keeping our own feelings at bay and seeing if there is merit in what they say can be helpful - you said your FIL has raised concerns known about the meds - asking him about his observations, letting him know that you are hearing him, noting them along with your own can be quite helpful for the treating team.
Having the outlaws as allies in the process can be helpful - the brother that said the things that upset me - along with another, travelled interstate to pick up Mr Darcy and bring him home to yet another state after he went awol (in what was likely undiagnosed psychotic depression). Mr Darcy's family is quite dyscunctional and we are the only ones who keep in touch with all of his brothers on a regular basis.
Hope this helps.
Darcy