How about if you write down what you need to express to her, then ask your mom if she has some time to talk.
Sit down with your mom and tell her that you are having difficulty knowing how to verbally express your concerns to her which explains your written feelings.
Hand what you have written to her and remain with her throughout her reading it. Allow her whatever amount of time she needs to read it without inturruptions, unless she decides to question something as she is reading.

Do your best to maintain composure and your best to refrain from becoming upset. Remember, that some of it may come as a surprise to her, so antisipate that sort of a reaction.

Perhaps too, that in your written expression of concern you can include how you are feeling uncomfortable with confronting her, (for whatever your reasons are). That alone will provide her an understanding of why you simply cannot verbally discuss it with her, and should create some easement into the entire matter for you both.

Keep us informed. We care what happens to you.

Thinking of you.....

Shangrala