Hi Emma Cross,
I'm glad you have taken the time to explain what has being going on for you and this particular friend of yours. I hear you say you used to be quite close and have know each other for quite some time. More recently it has been quite bitter, comparing her struggles to yours and acting extremely guarded and hurting your feelings. Consider you have know her for quite some time I imagine it would hurt the things she says, even if you know they are to be untrue - pretty anxiety provoking. It sounds like conversations with her don't leave you feel very good or heard, exactly the opposite maybe. If you are experiencing your own set of hardships outside of that relationship, the added stress is just not needed. COVID-19 is hard enough on its own. Life pretty upside down at the moment, are you still able to work and study?
With everything you have said so far and the track record of the interaction with this person, and how they have made you feel, no wonder why you are questioning opening the message! It almost sounds like you are questioning whether it is worth engaging in the relationship all together!? Which is totally understandable. Right now it seems like it's not adding to your heath and wellbeing, but at the same time having conflict with this friend is likely doing there same, and the not knowing of what she had to say anxiety provoking in itself.... thats tough to navigate.
You know what, maybe you aren't in the right frame of mind to engage in that conversation right now, and thats okay. You are allowed to have and set boundaries. That is not being a bad friend, that is called being as assertive and that is an amazing quality to have, especially when dealing with people who put their needs and wants before yours.
However thats not to say that in a hours, day, or weeks time you will feel different, or feel ready to have that conversation. Can I recommend giving yourself the permission, giving yourself the time to decide?