you might be surprised, but even if YOU think you dont have any milk left, you are producing milk constantly all the time, so there is no such thing as not having much milk left. theres always milk.
this is normal 4.5 month old behavior. stop expecting her to sleep all the time - 'sleeping like a baby" really SHOULD mean wakefullness and sleeping in short bursts. its a myth that babies can or should be sleeping through the night at any point. in all reality, this is a protection habit - it keeps them from falling too deep asleep, and helps prevent SIDS or other suffocation etc etc. so, if you can, be happy your kid is waking up.
www.askdrsears.com will be a great help for you. its normal, and healthy for a baby to wake often, especially to eat. this is the ONLY time in your child's life (we hope) that she will triple her weight in a year, and double her height. thats a LOT of growing, even if you dont really see it that way, that IS what happens. think of how often you would have to eat to triple your weight in a year!! so please, do your relationship with your baby a favor, and listen to all her cues, no matter how many times she needs to eat, she NEEDS to eat. shes not manipulating you, shes not lying in bed thinking about how she can get her way, whatever. try cosleeping, bedsharing (which are 2 different things by the way - bedsharing is exactly that, cosleeping is having baby in the same room as you in her own bed unless she needs to eat, etc)
those 2 things alone will help you. especially bedsharing, honestly, its not NEAR as dangerous as the "experts" would have it seem, the cases where a child has died in a bedsharing situation are actually already at risk because of alcohol use, drug use, or other siblings in bed, etc. its actually more safe because it allows both you and baby to nurse during the night and not actually be awake. this might make your husband uncomfortable, and if hes not comfortable with it, there is NOTHING wrong in your marriage if he sleeps in another room or on the floor during this time, or if you did those things. you do what you have to do to respect your child's needs and still sleep.
where were you when you were trying to get her on the bottle? most babies will not accept a substitute for the real thing if mom is there. they know better :P hahaha. they can SMELL you.
so if you really want to try to get her on the bottle, leave the room, have someone else do it. dont have that person sit in the same places you would sit to nurse her that will also remind her of the real thing. also, you dont say if this is a formula or pumping breastmilk switch, if formula you will have a hard time either way because babies dont like to drink formula for obvious reasons, it plugs them up, it doesnt taste good (have YOU tried it?!?) and it causes more gas and cramping for them. pumping breastmilk will be easier because it will be a normal taste for baby, and will make it more comfortable in the interum of you being gone. its not a detremental 'wanting you there' feeling as much as it will be a 'this is from mom' sort of thing. its like, you can be there without being there.
anyway.... you can do both. if you breastfed when you were home, and did formula when you are gone, that is acceptable, it will balance out the constipating, gassiness of formula and you will get to return to that closeness of nursing when you are home.
aynway, whatever you do, NEVER make a decision lightly (what mom does) and do whats best for YOUR FAMILY. no matter what i say, what a doctor says, what your own parents or inlaws say... you do what YOU and your husband feel is best for your family. i parented by stubborn instinct, i wasnt going to let ANYONE tell me what to do about my parenting. i breastfed on demand until my son self weaned at 19 months, and that worked for us. we bedshared for a while - until my son was between 15-17 months and slept through the night consistently. he still sleeps in a bed in our room. thats what works for us. if that all sounds foreign to you, tis because a lot of advice out there REJECTS these ideals as good family practices, and instead calls them manipulation, spoiling, and hurtful habitual parenting. instead they are attachment parenting techniques, built on the idea that babies need their parents, day and night, and the more you respond to a baby's needs, the more trusting they become of you, and the better relationship they have with you throughout their whole life. this isnt impossible with formula feeding! as long as you are present for the feeding, you talk to baby, you respond to all baby's cries and needs, and never feel like you have to let your baby cry.. it doesnt matter as much what you are feeding. a lot of people think that you have to breastfeed to be an attachment parent when thats not true. plenty of parents who cant do it just fine on the bottle, the key is to NOT listen ot any advice that makes you hurt inside, that makes you feel bad or upset, that makes you uncomfortable. you have the specific instincts for your specific child, and you should listen to THEM not outside advice.
having said that, ive blabbed long enough, have a good day, and good luck with the sleeping.