To the extent that gangs offer females a chance for self-respect, it is because the females have such poor family lives and such poor prospects that even being abused to some extent may seem preferable. At least if they are attached to a gang, they belong to something that is to some degree respected and which offers them some sort of an identity.
In situations where females join gangs, it is likely that they have very few good choices in life. Their choice is not between joining a gang and being abused on the one hand and having a good life on the other. Instead, it is between being in a gang and being abused and being out of a gang and still having a life of poverty and very little respect. In that sort of a situation, what is the real harm in joining a gang? At least as part of a gang they have some amount of status and they are with males who are respected. This might be the source of more self-respect than they would gain if they were not in the gang.