If you don't feel comfortable riding her, then I would suggest that you don't! She will pick up on your nerves and insecurity and, more likely than not, take advantage of that! Maybe work on lounging instead, and then after a few days of that, move to leisurely riding. :)
The hills were bathed in moonlight, the shadows not so stark;
Silver light reflected off his brown hide as he held me in the dark
– I love you, Mudpie!