Since you asked if there were any agents on here and wanted their opinion as an agent I thought I would chime in. I'm a local broker and have been in property management for a long time in the area. (not for this property luckily. If I am, the property manager has kept me out of the loop!!!) First, I completely understand why from your side of things you would be upset and peeved at the agent. You do have to remember though, they are one set of tenants out of hundreds or thousands (depending on the co) that this agent may be the property manager for and the agent does not know your or your kids like you do. Knowing your girls and the situation it seems clear cut to you that a $25 a month increase per tenant would never be enough for them not to renew.
I can tell you from experience though, that that is definitely not the case. Also, no response is college kid speak for "no: or "I am not ready to make a decision". Since they never responded after the email with the price increase I don't think there is any way you can expect the agent to make a determination as to whether that amount is significant enough for them to not renew or not. I would say out of the tenants who tell us "yes we want to renew" only about 50% of those actually do. Not 50% of tenants, 50% who say in the fall they want to renew the next year. It happens because of a variety of reasons. A student fails out, roommates fight, they find a place closer to their friends, on and on and on. I have had tenants I trusted lead me on for months saying they were going to come sign the extension only to tell me in July "oh sorry we found another place that works better for us".
The last thing I would say is the statement "The realtor is the grown up in the relationship, and I expect much more out of her than we received." is a little one sided in my opinion. I believe you said the girls were 21 or so. Both parties here are grown ups. If you sign the lease and live on your own it is not the job of the agent to be the grown up for the students" I know that sounds harsh but I would bet this agent has allot of properties they manage. I doubt there was anything on purpose here to try and screw the girls out of a house (its a whole lot easier on the management co to keep the same tenants and make readies suck) I am guessing they were just really busy, checked the file and said "they never emailed us back or returned the extension so we need to get this leased". Anyone over the age of 18 who signs a legal contract is responsible for what they sign and knowing what they signed. I honestly cant tell you how many times I have had a conversation with a tenant who is arguing about something that is clearly stated in the lease. They have actually said to me "I'm a college kid, you cant expect me to read the whole lease and know what is in it" and my answer is "absolutely I do". The contract is what is there to guide the transaction. Both sides should know what was in it and be aware of the terms.
I will say, it really sucks for your daughter. I am surprised they are just now finding out about it. It is not required but normally once we rent the property to another tenant we send some sort of notice to the current tenant. Again, not required, but we just want to make sure they are on the same page. I also know this late in the game it is tough to find a good place and that adds allot of stress to it. I hope you guys can find something that works out for everyone. There is always stuff that comes on last minute when a group of tenants bails out so who know you may even luck out and get something cheaper.