Trusting future SiL

'Encouraging' a partner to give up their car is a well known method of coercive control, especially in rural areas. The excuse that it saves money is hard to argue with if finances are a bit tight. Being taken everywhere means surrendering independence which is hard to get it back once it's gone.

Starlady, I believe the OP's daughter is drinking in secret, not socially. Knowing it will cause a row if discovered is her way of trying to keep some control over her life.

Why on earth is she still with him?

I'm another one who understands your being concerned, OliverZach, if you feel DD's fiance is controlling. I don't blame you for approaching her about emotional abuse if you fear this is the case. If she doesn't see it, though, nothing you say will make her.

"We as a family drink socially. DD has taken to drinking in secret but gets found out which results in rows & accusations."

I'm a little confused. Ive never heard of "secret social drinking." To be "social" a drink has to be taken around other people. When someone hides their drinking, it is usually a more serious issue. It sounds as if there's a deeper problem here than you realize, but perhaps her partner just doesn't know how to handle it.

"What do I do?"

Hard to say b/c I'm not clear on what's going on or whether DD is really just drinking socially or not. Does DD's partner appear to be controlling in any other way? You say she has lived w/ him for "many years." Did he always seem controlling or is this of recent vintage?

Stella, maybe she didn’t ‘choose’ to give up her car. We don’t know because the OP hasn’t told us.
Even if they only have one car now she should be able to go out in it on her own.
We have 2 cars they are ours, not his and mine.

. DD gave up her car (can’t go into reasons why) & now he takes her everywhere. Seems good on paper but she has no “free” life

I can't really see that this is his fault or that he is controlling. If someone gives up their car and then relies on their partner to take them everywhere, that's up to them really. Why doesn't she use public transport if this arrangement is cramping her style ?

He abhors alcohol, problems as a youngster? We as a family drink socially. DD has taken to drinking in secret but gets found out

Regarding the drinking - she comes from a drinking family, but now lives with and is going to marry someone who abhors alcohol. Once again, her choice , she knows he hates it. But instead of talking to him about it or coming to some arrangement to "agree to disagree" about alcohol, she is drinking in secret which then leads to fights.

Sorry but I can't really see that her partner is controlling her - more that she has made some choices in her life which she now finds stifling. Choosing not to drive / getting him to drive her everywhere , and drinking in secret , are her choices, not his.

My thought is that she needs to look at her relationship . Instead of planning a wedding she might be better off reviewing whether they are actually suited as a couple.

Has she been pushed into setting a date? Doesn't she see any red flags at all?

I'm glad you and she still talk, that's a good sign but being forced to hide a social drink is not.

I think you're right to be concerned about emotional abuse by potential spouse which often turns into estrangement or, god forbid, physical abuse.
Can you offer to pay for family counseling to address these issues with a professional?