It’s not her fault that she had this option available to her.
It sounds to me like you wish you had the same, or that also suffered as much as you did.
Your friends circumstances do not detract from nor improve yours, you are separate families, not even related.
By that logic, you can go ahead and be jealous of everyone else you know who has something you want desperately, maybe that’s already the case.
It’s your life, you can ruin your own happiness however you wish. Jealous people often do end up with less, it’s a self fulfilling cycle.
How about if you were happy for your friend in a time when she may have been struggling even worse than you were... key workers were not given this option because they have an easy life!
Happiness for others tends to rub off on us, and you never know, your friend may help you out if a difficult situation sometime.
I do feel sorry for her, there she is inviting you out for lovely walks and coffees, and you are seething because for a short while her life appeared easier than yours. If she knew, she’d be very hurt. Have this thought about that? Maybe it point is that you did want her hurt - jealousy is a very hostile feeling.
You are better than this, it doesn’t have to be this way, look at things from a more positive logical perspective. You can definitely work through this if you try not to indulge that thought process and feeling which doesn’t serve you.