Notsooldat75, I would agree with people who have already posted that it is important for you to step back from this friendship and concentrate on looking after yourself and working your way through the feelings you have associated with your own recent bereavement. Grief presents in many stages or layers and you need the space and time to focus on your own well=being. It must be hard on you having someone you love and/or care about die and then have to deal with strong, negative and unpredictable reactions from someone with their own struggles. I think you have it right when you tell us she avoided you by 'giving you space' so therefore 'giving her space' is a logical option.
It sounds as though your friend runs to you after her husband gives her a hard time, then projects that hurt and anger on to you. Whilst friends may use each other as sounding boards at times, this is a two-way street. This woman is so wrapped up in everything going on in her life, her household, her relationship/marriage that maybe she cannot see how she is making you feel, how badly she is reacting to helpful, well-meaning suggestions and there is no reason you should just accept the snorting and eye rolling, as that wouldn't be a nice thing to do under any circumstances.
Maybe next time she turns up unannounced tell her it is not convenient - or drop a note through her door before this happens just explaining you need space for your own grief and understand she may need space for her issues! Say because you need time to adjust you are no longer able to entertain people at random and expect people to respect this by calling first to check it is convenient or that you don't already have plans in place if they don't have a prior agreement for a visit. Be firm though as it sounds like strong hints would fall on deaf ears.
When this woman is ready to tell family, ask for help, call in professionals or support organisations she may get that help and support but until then there's not a lot you can do without being her 'emotional punchbag'. She is responsible for her life and her decisions but they shouldn't make you miserable, anxious, depressed etc.
Please do take the time to care for yourself, to get any support you need, and spend time with people that care enough about you to provide support, shoulders for you to cry on, safe space to just sit, to have a cuppa, a socially-distanced walk etc. And if shielding or not seeing many people in the current Coronavirus climate, there is always Gransnet - for the most part I'd say this is a helpful and supportive forum and we can offer some moral support if nothing else. Best wishes, stay safe and take care of you