No, that is not healthy. It is also stupid - you should realize that your have mutually exclusive requirements, and your having mutually exclusive requirements is YOUR problem and not her problem.

If you want young and blonde, and are more-or-less in touch with reality, you should realize that many other guys would like young and blonde too. Not all, but many. As per the 1953 movie, Gentlemen Prefer Blondes (1953) - IMDb - it is a classic movie and if you have not watched it, you should do so ASAP.

In other words, your wanting your gf to be young and blonde is not something highly unusual and unique to you ALONE.

Therefore, if you want a gf who would never be checked out by other guys, you clearly should drop the idea of "young and blonde" altogether and for the rest of your life.

To summarize your requirements, as I am able to distill them from the quoted part of your OP, above, you want her to be "young and blonde" only to YOU, but not to other people. For that, she would need magic powers.