I'm reading between the lines here, but here's my take.
1. Since you don't have a contract with any agent or agency, you don't have an agent.
2. At some point in time, your first YA work was represented by an agency and an agent, but your contract with them has expired without renewal.
3. I'm assuming that your former agent did a fairly thorough job shopping your first work with editors but wasn't able to sell it. Also, at some point -- I assume when s/he decided not to renew your contract -- you were made aware of suggested, numerous re-writes.
4. Your former agent (is she still with the agency?) has offered to be your "career" agent, whatever that is. Career, as you well know, means ALL you do in the profession, not just one book as seems to be the case. It sounds like you want to have her around, and that's obviously your call, but why not make her your Manager for everything you do in publishing, if that's possible? Of course this means another percentage of anything you may earn.
5. I have no knowledge to back this up, but if I'm right and your first work has been well shopped. I'd forget about it for now and concentrate on the second book. Look for a new agent based on your second book. Of course you'll have to mention the termination with the first agency, but be sure to mention that your new work hasn't been seen by any publisher.
6. I think you're continued involvement with the first agent and your first work is clouding your judgment, and in a way may be holding you back.
Good luck.