I think that it is perfectly appropriate to email someone that worked with you. You don't have to tell her that you have a crush on her. Just write a note saying "Hello" and asking her how she has been. If she replies, then you know that she is at least friendly towards you. Exchange a few emails and find out what is going on in her life. Eventually, you could ask her if she is seeing anyone and, if she isn't, ask her if she would like to do something with you sometime. As for getting her attention and not having your email deleted, personally, I know which emails are spam and which ones are from personal email addresses in my inbox. If she doesn't reply to your email the first time, try again, and explain that you wanted to make sure that she received your email. Good Luck.