She is jealous of your relationship (still have a husband) and you are jealous of her financial stability. It sounds like you feel sorry for her because she lost her husband, but resent her for having money and not having to work. This is not a friendship - you should end it quickly before she discovers how you really feel about her.

Your friend seems heartbroken and lonely and obviously isn't coping well with the loss of her husband. You've been sweet up until this point but it seems like your a bit over it. I would maybe suggest she gets a part time job or work at a local community centre or the like so she is out of the house, busy and meeting new people everyday. My heart breaks for her and her loss and it does seem like you've been an amazing friend. I would maybe recommend introducing her to other people - maybe go to bingo or dance classes or something and try to get her to meet new people and make other friends so it's not so demanding on you all the time. Best of luck x

I think she might have let the money go to her head.. hence the rudeness on your holiday. Anyway, now that her husband has passed away, you probably won't be going on any more holidays with her in the future.
As for the deer.. sounds like a bargain, but i am guessing she is trying to gain self worth through money, and there is not much you can do about that.
As for the Sunday night thing.. just send her a text on Saturday morning saying that your husband has gastro so no visitors this weekend please. The following week tell her it's a busy time of the year and you're catching up with other friends this Sunday night so sorry to break the special routine 2 weekends in a row. If she is one to drive by your house and mentions there were no extra cars there, tell her they got an Uber so they could consume alcohol.
The weekend after you could suggest going to her place.. stay for a bit and then leave early.
The weekend after that it will be only 2 weeks until xmas so tell her you are busy doing deep cleaning and getting ready for xmas. Then it will be xmas. In january tell her you are going to the beach etc. See her occasionally and if you want to maintain the friendship at all costs, you will need to put up with her behaviour . If you are willing to risk losing her friendship then you will have to have a conversation citing some specific examples of how it makes you feel when she says/does what she does. e .g. when you tell me X it makes me feel X. When you speak to me like that i feel X.
Good luck

Ok, so why be friends with her? Obviously her coming over to your place every weekend to watch boxsets is a symptom of her grief. But you mentioned that she was horrible when you were in holiday, I’m presuming when you went away before her husband died.