Forcing Friendship

Well don't know if that made me feel better or worse.   I have a friend who I thought was a pretty decent friend.  We worked together and got together outside of work.  In January things got kind of weird as she ended up being my boss.   She didn't have time to do the job and I tried to help her with it.   Sometimes she got mad as I didn't do enough of what she needed help with and sometimes she got mad that I was doing too much.   I was very worried the friendship was destroyed when she came up to me and asked if I wanted to walk in the mornings like we did the year before.
I was elated.  We were ok.  I was making too much out of everything.   Said yes and we talked about schedules.  Then the first week I called her and she said no she was too busy.   Didn't think much of it as we were getting together for another activity.   Then this week she didn't contact me.  Figured she was still busy, so I sent her a note asking about next week.  Got told she walked every day this week.  What....but why didn't she invite me to go.....
So said oh you must have finished cleaning your garage and she said no she only had two trash cans so could only do so much.  I tried to make a joke about her being gone the week before and got a kind of harsh comment about it wasn't being gone too much it was lack of trash cans.   I wasn't sure what I said wrong, but tried another joke about throwing away money instead of stuff as we had gone gambling the week before.   She stopped responding to my msgs completely.  So texted her daughter and tried to talk to her.  Asked her about walking and got a weird comment when asked how long they walked and then said I could only do Thursdays as I work Mon-Wed and she stopped talking to me too.
Checked back for 2 hours and neither of them said a word to me.  I was so upset.  DOn't know what I did.   Upset all night and woke up this morning feeling horrible.   Can't sit, can't do anything, pacing, feel sick.  Finally called her and asked if she was walking today.  She was so I invited myself along.   Just told her I was coming over.
So we walked and the first couple comments I made were met with ice.   I told her I was just joking about the gambling and she didn't respond.   Said I would have walked with her a different day if I'd known they were going, but she hadn't mentioned it and got just a oh well out of her.   Changed the subject and by the end of the walk we were talking normally.   I thought about asking her if she was upset with me and why, but just couldn't do it.   Things seemed ok by the end so I let it go.  Don't know if I should have. 
Right before I left I told her I could walk on Thursday and did she want to.   Got what sounded like a half hearted yeah we can do that.   Don't know if I am doing the right thing.  Feel like I am forcing her to be friends with me when she doesn't want to.  Guess I should have asked what was wrong.   At the same time I am hoping we can get back to being friends if we spend time together and maybe she will get over whatever the problem was.
I have so few friends I can't stand to lose any more.  Just feel like I was die.   I actually took the scissors out last night and scratched at my arm.   Just made a red mark.  I was never a cutter, but sometimes when life was really upsetting me I would make like cat scratches.  I think I have only done it one other time in the last 20 years.   I am really falling apart and I need this friend.   Wish she needed me.