Odd behaviour while in heat

We recently took in two bonded cats, the female is 4 and the male is 3 (he is fixed). They warmed up to us really quickly. Over the last week the female has started going into heat. Now that she is, she is getting aggressive towards the male cat, has hissed at my daughter, is losing hair on her legs and she pee'd on my bedroom floor. This seems like really erratic behaviour for her being in heat? She is still lovable with me but isn't overly so, and she doesn't howl like a regular cat in heat, all she has started doing is the combat crawl with her bum in the air and the behaviour changes. 

Any advice?

None of what you describe is unusual or erratic behavior for an unspayed cat.

I would recommend spaying her as soon as possible.  the longer a behavior goes on the harder it is to stop.

I would tend to think that most of it will disappear once she is spayed.

If you need any other reasons, cats who are not spayed have a much greater chance of getting certain types of cancer.

If money is a problem, most places have low-cost, if not free, spay and neuter clinics or programs if you search for them.

Count your blessings that she is not howling. The thing is, she will constantly come into heat, every couple of weeks with a week (maybe-if you're lucky) off.  It's really for her benefit physically to have her spayed.  So many health problems.  It concerns me that someone let her go 4 years without getting spayed?  Do not be surprised if she has pyometra (an accumulation/infection of puss in the uterus).  It can be quite serious and life threatening.  It happens when you leave a female intact and she continually comes into heat without being able to mate and get pregnant.  However the sooner you get her spayed, the better for her. 

People often think "Oh I'll get the male fixed because it's cheaper and then she won't get out so I don't have to worry about kittens."  Not so.  If she does get out, it takes only a few seconds for them to mate and get pregnant.  

There are low costs options in most of the USA, so I would look into them ASAP. 

She is getting spayed, that was never part of the problem. I have only had her for 3 weeks, and was originally told when I took her and her brother in that they had both been fixed...which is obviously not the case. She is booked to get fixed in the new year, which with the Holidays is the soonest I could get her in. She is fine now that she is no longer in heat thank goodness. 

That is good.  It's a common problem at adoption centers.  We have people surrender cats and swear they are fixed only to due a check up and find out they are not.  *Rolling my eyes*  Some people! 

 I understand you did not create this situation and had only recently adopted the pair, and it was not great that you were not given all the right information about the cats.  Although, to give the benefit of the doubt, I've heard of spayings going wrong in the past and needing to be done a 2nd time.  You'll know for sure once she is seen by the vet.

But her not being spayed is probably the main reason for the problem, the behaviors you described are most likely a direct result of her going into heat which will stop when she's spayed.  I'm really glad to hear you have an appointment to do so. 

If she goes into heat again before your appointment, the behaviors will probably return, only to stop again when she goes out of heat.  Once she's spayed, no heat cycles, the behaviors should go away, hopefully completely, and for good.