Yes Manglik can marry a non Manglik.

Can Mangal Dosha be removed?

If both the partners are Mangliks then this dosha gets nullified. All its ill- effects are cancelled and the two can have a blessed and happy married life. When one person is Manglik in a marriage, the negative effects of Mangal dosha can be cancelled by performing this ritual called Kumbh Vivah.

How can we know girl is Manglik?

Mangal Dosha is seen through the Lagna Chart, Moon Sign Chart and Venus Chart. If Mars occupies above houses in ones natal chart, then it will be considered as High manglik Dosha. If it is occupying these houses in any one of these charts, then it will be considered as Low Manglik Dosha.