Alaikumassalam wa rahmatullah,
Manhaa, the way you spelled it in Arabic, means forbidden act, anything that is prohibited, it is not used as a name by Arabs since it doesn't have good meaning.
There is another word that sounds like Manha (spelled as منحى) and it means "path", "road". For more information on this one see this answer: Meaning and pronounciation of Manha
Ibtihal means to pray and supplicate humbly in front of Allah. It is not used in the Quran directly or indirectly, but the meaning is good so it can be used by Muslims. It is pronounced as (I)slam + (B)eau(TI)ful + (HA)rd + Is(L)am
Hasan means beautiful. You shouldn't spell it with two "S"s because there is no stress on the "s", it is pronounced as (HU)mble + (SUN). There is another name, Hassaan, which has a meaning similar to Hasan and is spelled as حسّان.
Manha Hasan (the second Manha which means gift from Allah) and Ibtihal Hasan are good and acceptable names for Muslim girls.
Mahd means cradle, place where something is born or begin, and an area of earth that's flat with no roughness. It is a direct Quranic name.
Ihab [pronounced as (I)slam + (HA)rd + (B)oy and also as (EE)l + (HA)rd + (B)oy] means blessedness, a blessing and power given to you. It is an indirect Quranic name.
Mahd Hasan and Ihab Hasan have good meanings and you can use them.