Wow she looks so different with her hair down! I love it 
Little quick translation of what she wrote in her first blog post:
She introduces herself as the 16th gen member of Momusu and writes down a few things about her.
New to us: Her favorite food is curry, but she can't handle hot curry so she prefers butter chicken. Her favorite sport is dodgeball but she likes ball sports in general.
When she heard that she had passed the audition, she didn't really feel like she really passed, but when the official announcement to the public happened, that's when she realized it was true. She expresses her happiness to be part of the Hello!Project she loves. She's a little worried because she's the only one in her generation, but she wants to work hard.
She ends her post with the words "日々前進あるのみ" which are a little hard to translate. It basically means "There is progress every day", but also kinda like "Just keep going every day!". It's an interesting phrase and I'm not sure how to translate it, but for me, it gives off the feeling that Rio is kinda smart and good with words. 
Since her announcement I have been thinking about what it must be like for her to join a group alone as a kouhai, when the senpai closest in age have 3 years more experience than you. It's definitely not easy, so I really wish her all the best so she can catch up. I'm cheering on her 
By the way: After her first blog post, the hashtags "first blog" and "Sakurai Rio" were trending on Twitter. 
Source: https://twitter.com/...689837580357635